-------- Forwarded Message --------
Subject: [Security-announce][CVE-2026-11940] tarfile extraction filter bypass
allows escaping the destination directory
Date: Tue, 23 Jun 2026 16:55:19 +0100
From: Stan Ulbrych via Security-announce <[email protected]>
Reply-To: [email protected]
To: [email protected]
CC: Stan Ulbrych <[email protected]>
There is a HIGH severity vulnerability affecting CPython.
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.
Please see the linked CVE ID for the latest information on affected versions:
* https://www.cve.org/CVERecord?id=CVE-2026-11940
* https://github.com/python/cpython/pull/151559
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