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Message-ID: <1889c8ad-70d3-44dd-9914-53fbbd17fffc@oracle.com>
Date: Tue, 23 Jun 2026 09:32:32 -0700
From: Alan Coopersmith <alan.coopersmith@...cle.com>
To: oss-security@...ts.openwall.com
Subject: [CVE-2026-11940] Cpython: tarfile extraction filter
bypass allows escaping the destination directory
-------- 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 <security-announce@...hon.org>
Reply-To: security-sig@...hon.org
To: security-announce@...hon.org
CC: Stan Ulbrych <stanulbrych@...il.com>
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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