CVE-2026-12345

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.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

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