Package Instance

virtualenv Has TOCTOU Vulnerabilities in Directory Creation
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