CVE-2026-11940

Summary

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.

Affected Software

Weaknesses

• CWE-22: CWE-22
• CWE-59: CWE-59

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: partial

References

• https://github.com/python/cpython/pull/151559
• https://mail.python.org/archives/list/security-announce@python.org/thread/LD6QIISNQFQYOIEPJNEUIPV7S3V76FZH/
• https://github.com/python/cpython/issues/151558
• 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/commit/be13e86f6b9788a6f4d0419dffef72cbae5865c9

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