CVE-2026-11940

Description

tarfile.extractall() with the 'data' or 'tar' filter could be bypassed by a crafted archive where a hardlink references a symlink stored at a deeper name than the hardlink itself.  The extraction fallback validated the symlink at it's archived location but recreated it at the hardlink's shallower path, letting a relative target the filter judged contained escape the destination directory.  This allowed a malicious tar archive to create a symlink pointing outside the destination, enabling out-of-destination file reads or writes. This was an incomplete fix of CVE-2025-4330.

References

• https://github.com/python/cpython/commit/27dd970bf6b17ebca7c8ed486a40ab043ed7af8f
• https://github.com/python/cpython/commit/672825e2f36a57e173959b0d9d409d4560dab8df
• https://github.com/python/cpython/commit/771d12dda5140313db0ac550292987975651bbde
• https://github.com/python/cpython/commit/79c06bd5c6afa3c440d50faf7ee1b147c8832b4c
• https://github.com/python/cpython/issues/151558