virtualenv Has TOCTOU Vulnerabilities in Directory Creation
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_DATApoints to a directory owned by the current user with restricted permissions (mode 0700) - Avoid running
virtualenvin 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
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | virtualenv | < 20.36.1 | 20.36.1 |
References
- https://github.com/pypa/virtualenv/security/advisories/GHSA-597g-3phw-6986
- https://nvd.nist.gov/vuln/detail/CVE-2026-22702
- https://github.com/pypa/virtualenv/pull/3013
- https://github.com/pypa/virtualenv/commit/dec4cec5d16edaf83a00a658f32d1e032661cebc
- https://github.com/pypa/virtualenv
- https://pypi.org/project/virtualenv
- https://github.com/advisories/GHSA-597g-3phw-6986
- CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L- Weakness (CWE)
CWE-362, CWE-59- Platform
- Python (PyPI)
- Package
virtualenv- Disclosed
- 13.01.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2009 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-597g-3phw-6986 - CC BY 4.0
Vulnerability history: virtualenv
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 12.2011 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 3
Disclosures per year
- 2017: 0
- 2018: 0
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 1
- 2025: 0
- 2026: 5
earlier: 1
-
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