Vulnerability in Python Software Foundation CPython

[ Description ]Official description

The cleanup of tempfile.TemporaryDirectory is vulnerable to a race condition. An attacker who can modify the tree during cleanup can replace a directory with a symbolic link, causing files outside of the temporary directory to be deleted or have their permissions and file flags reset, with the privileges of the process performing the cleanup. Note that platforms where shutil.rmtree.avoids_symlink_attacks is false, remain affected, and file flags may still be reset outside of the tree on all platforms.

[ Fixes ]Fixes and patches

• Security bulletin: Python PSF-2026-42Vendor patch or bulletin · CERT-FR · raw.githubusercontent.com/psf/advisory-database/main/advisories/python, cited by CERT-FR CERTFR-2026-AVI-1239

[ Advisories ]Government CERT advisories

• CERT-FR30 Sep 2026CERTFR-2026-AVI-1239

  Vulnerability in CPython Translated from French

  A vulnerability has been discovered in CPython. It allows an attacker to cause a breach of data integrity.

  CVE-2026-12345
• BSI CERT-Bund29 Sep 2026WID-SEC-2026-3656

  CPython: Vulnerability allows bypassing security measures and file manipulation Translated from German

  Risk mediumCVE-2026-12345

[ References ]References

• github.com/python/cpython/commit/06ef3d43fdaf4da97af12fa694b4886092c4b970
• github.com/python/cpython/commit/458e7134a5af7f86aee9d21b51cf499b41aa4420
• github.com/python/cpython/commit/58ed0259cae509a19138795df302fe60b544dc74
• github.com/python/cpython/commit/5c20517a4fc56683efe63a7751020db9573f538d
• github.com/python/cpython/commit/e1f3590f155c6d66007e958c98c9d69316551993
• github.com/python/cpython/issues/157579
• github.com/python/cpython/pull/157580
• www.openwall.com/lists/oss-security/2026/09/29/40