The vulnerability arises when virtualenv uses Pip seeder with the --download option. The code path bypasses virtualenv’s verify_wheel_digest, allowing a wheel from a non‑PyPI index to be installed without SHA‑256 verification. Based on the description, this could enable a malicious wheel to be chosen while still satisfying the default digest‑verification policy, allowing tampering of package contents and compromising the integrity of the virtual environment. The weakness is classified as CWE‑494: Unverified Stored Credential or Downloaded Content not Validated.

pypa’s virtualenv prior to version 21.14.9 is vulnerable. Users running virtualenv 21.14.8 or earlier who use the Pip seeder with the --download flag on a non‑PyPI index are affected. The issue has been resolved in 21.14.9 and later releases.

The CVSS score of 2.3 indicates low severity, and no EPSS score is provided. The vulnerability is not listed in the CISA KEV catalog. Based on the description, the practical risk depends on the use of a custom package index; if the index is malicious or compromised an attacker could replace wheels while the integrity check is bypassed. An attacker would need to control or influence the package index to introduce malicious code. Assuming typical deployments rely on public PyPI indices, the risk is modest, but the integrity of the environment remains at risk if the pip configuration allows the insecure --download seeder flag.