GHSA-597g-3phw-6986
MEDIUMvirtualenv Has TOCTOU Vulnerabilities in Directory Creation
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
virtualenvReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | virtualenv | all versions | 20.36.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for virtualenv. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update virtualenv to 20.36.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-597g-3phw-6986 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-597g-3phw-6986 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-597g-3phw-6986. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-597g-3phw-6986 in your dependencies?
O3 detects GHSA-597g-3phw-6986 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.