Vulnerability in Python
CVE-2026-4224
When an Expat parser with a registered ElementDeclHandler parses an inline document type definition containing a deeply nested content model a C stack overflow occurs.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.012 (67.3th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 67th percentile — 67.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.012 · change: +0.005
Affected products
- Python — versions 3.15.0
- Python Software Foundation Cpython — versions 3.14.0, 0, 3.13.0
Weakness classification (CWE)
References
- github.com/python/cpython/commit/eb0e8be3a7e11b87d198a2c3af1ed0eccf532768 (Patch, patch)
- mail.python.org/archives/list/security-announce@python.org/thread/5M7CGUW3XBRY7… (vendor-advisory, Third Party Advisory)
- github.com/python/cpython/issues/145986 (issue-tracking, Issue Tracking)
- github.com/python/cpython/pull/145987 (Patch, patch)
- github.com/python/cpython/commit/196edfb06a7458377d4d0f4b3cd41724c1f3bd4a (Patch, patch)
- github.com/python/cpython/commit/e0a8a6da90597a924b300debe045cdb4628ee1f3 (Patch, patch)
- github.com/python/cpython/commit/642865ddf4b232da1f3b1f7abcfa3254c4bfe785 (Patch, patch)
- github.com/python/cpython/commit/af856a7177326ac25d9f66cc6dd28b554d914fee (Patch, patch)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)
- github.com/python/cpython/commit/24ce88b285f56ee11626cf5e472af3cd8cc7c621 (patch)
Frequently asked questions
- What is CVE-2026-4224?
- CVE-2026-4224 is a high-severity vulnerability in Python, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-03-16.
- How severe is CVE-2026-4224?
- High severity. CVSS v3 base score is 7.5 out of 10.