What’s Vulnerable › Vulnerabilities
CVE-2026-87910: tarfile hardlink fallback ignores custom extraction filter rejection via None
- Severity: medium (CVSS 5.7 v4.0)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.6% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-09-11 · updated 2026-10-22
- Weakness: CWE-22
Description
When tarfile extracts a link on a system that doesn't support links, it falls back to extracting a member from the archive. In this case, the filter function is run twice: once for the extracted member, and once with name set to the location of the link. For one of the calls, the return value was ignored. Instead, the member should be skipped if either call returns None.
Affected products
- Python: before 3.10.22; from 3.11.0 before 3.11.17; from 3.12.0 before 3.12.15; from 3.13.0 before 3.13.16; from 3.14.0 before 3.14.9; from 3.15.0a1 before 3.15.0rc3 — fixed in 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.9, 3.15.0rc3
How to fix
Upgrade to a fixed version: Python 3.10.22, 3.11.17, 3.12.15, 3.13.16. Check the vendor advisory for mitigations.
References
- https://github.com/python/cpython/commit/2eb0c2f1dc71847731b6ab30aebefd058d482a7f
- https://github.com/python/cpython/commit/3105a3498aaf681ce128cf5baf83c2e5574267c5
- https://github.com/python/cpython/commit/764fd0af8d9e19d3684a58d2e58bf770f0605036
- https://github.com/python/cpython/commit/9c17bace90f88dfba6d0e2fe23c8e7ae35f83955
- https://github.com/python/cpython/commit/a4919937a4e1e69a0d178909c6f20557eca5d1d0
- https://github.com/python/cpython/commit/c1f106d240c4ffcb3608ed0a20e8aba6c865f6d3
- https://github.com/python/cpython/commit/d9565e54b1fc6d63c5be9afd58114499128fa57b
- https://github.com/python/cpython/commit/fb2f0bbc3b35264f09cc2cb2934b7987527a6bc2
- https://github.com/python/cpython/issues/157265
- https://github.com/python/cpython/pull/157266
- https://mail.python.org/archives/list/security-announce@python.org/thread/57TBTLL2W6APMZR3A25B2YV7GL3EPTDJ/
- http://www.openwall.com/lists/oss-security/2026/09/11/8
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