tarfile extraction filter bypass allows escaping the destination directory

7.8 / 10

HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

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.

Basic Information

ID CVE-2026-11940

Source PSF

Published Jun 23, 2026 at 16:04

Modified Jun 23, 2026 at 17:57

Affected Product

Vendor Python Software Foundation

Product CPython

Affected Versions Python Software Foundation CPython 0

CWE Classification

CWE-22 CWE-59

References

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    "lastseen": "",
    "description": "tarfile.extractall() with the 'data' or 'tar'\n filter could be bypassed by a crafted archive where a hardlink \nreferences a symlink stored at a deeper name than the hardlink itself.\u00a0 \nThe extraction fallback validated the symlink at it's archived location \nbut recreated it at the hardlink's shallower\npath, letting a relative\n target the filter judged contained escape the destination directory.\u00a0 \nThis allowed a malicious tar archive to create a symlink pointing \noutside the destination, enabling out-of-destination file reads or \nwrites. This was an incomplete fix of CVE-2025-4330.",
    "published": "2026-06-23T16:04:17.321Z",
    "modified": "2026-06-23T17:57:32.525Z",
    "type": "cve",
    "title": "tarfile extraction filter bypass allows escaping the destination directory",
    "source": "PSF",
    "references": "https://github.com/python/cpython/pull/151559\nhttps://mail.python.org/archives/list/[email protected]/thread/LD6QIISNQFQYOIEPJNEUIPV7S3V76FZH/\nhttps://github.com/python/cpython/issues/151558\nhttps://github.com/python/cpython/commit/27dd970bf6b17ebca7c8ed486a40ab043ed7af8f\nhttps://github.com/python/cpython/commit/672825e2f36a57e173959b0d9d409d4560dab8df\nhttps://github.com/python/cpython/commit/771d12dda5140313db0ac550292987975651bbde\nhttps://github.com/python/cpython/commit/79c06bd5c6afa3c440d50faf7ee1b147c8832b4c",
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}

tarfile extraction filter bypass allows escaping the destination directory_CVE-2026-11940