What’s Vulnerable › Vulnerabilities

CVE-2026-15310: zipfile: bzip2/LZMA/Zstandard members decompress without a max_length bound, defeating chunked-read memory limits

• Severity: low (CVSS 2.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-25 · updated 2026-10-02
• Weakness: CWE-400

Description

When decompressing crafted zip files using the bzip/LZMA/Zstandard compressions, Python could use an attacker-controlled size to pre-allocate memory, possibly resulting in memory exhaustion.

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 3.14.8; from 3.15.0a1 before 3.15.0rc2 — fixed in 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8, 3.15.0rc2

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/09a2e7e6678b4f65449e7ad8f112c48f944591e2
• https://github.com/python/cpython/commit/1b424c0178a01e155fd0267dc28a8fc1159b33a8
• https://github.com/python/cpython/commit/31980e84b9a708424a0a1dfecde3fc991e313f89
• https://github.com/python/cpython/commit/6257029de42ef89b67f3d20137de87d43e197530
• https://github.com/python/cpython/commit/9d167992b59cf5e23c66b9ed742b13f5925f7d70
• https://github.com/python/cpython/commit/c2bfbcdd1a11690507a10bc0998f95b8dc6b6fac
• https://github.com/python/cpython/commit/dcdd406ddbfc4cb29b24c3df17cbabe21d316ce1
• https://github.com/python/cpython/commit/e2311cfb3dd518f008f312fe0631f4f7490d237a
• https://github.com/python/cpython/commit/f507e6946a3194e83e1d7b8ee6e14567175e46de
• https://github.com/python/cpython/commit/f897dbf2f36a5935700b7c2d94d4681d2136b7d4
• https://github.com/python/cpython/issues/156002
• https://github.com/python/cpython/pull/156003

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