virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.9, download_wheel() writes package-index downloads directly into the reusable wheel/house cache before selecting a verification target from pip's textual Saved output. With default-index digest comparison enabled, a controlled package index can inject a misleading Saved line through a discarded link's data-requires-python attribute; this forged-line variant also requires knowledge of an absolute path to the genuine bundled wheel. The wrong path can then be hashed, while a digest mismatch leaves the rejected archive in the cache for later selection without verification. A separate rejected-cache-file variant requires control over downloaded data or archive selection but not the forged-line prerequisites. Explicit custom-index exceptions are outside the promised PyPI comparison, and the issue does not independently bypass TLS or establish control of default PyPI. This issue is fixed in version 21.14.9.
https://github.com/pypa/virtualenv/security/advisories/GHSA-494p-63j8-28p3
https://github.com/pypa/virtualenv/releases/tag/21.14.9
https://github.com/pypa/virtualenv/pull/3430
https://github.com/pypa/virtualenv/commit/7babec66e043e1cc8bc66869a063653898719d96
Published: 2026-10-20
Updated: 2026-10-20
Base Score: 5.8
Vector: CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:N
Severity: Medium
Base Score: 7.4
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Severity: High
Base Score: 2.3
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
Severity: Low
EPSS: 0.00212