What’s Vulnerable › Vulnerabilities

CVE-2026-4224: Stack overflow parsing XML with deeply nested DTD content models

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-16 · updated 2026-08-13
• Weakness: CWE-674

Description

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.

Affected products

• Python: before 3.10.0; from 3.13.0 before 3.13.13; from 3.14.0 before 3.14.4; 3.15.0-alpha1, 3.15.0-alpha2, 3.15.0-alpha3, 3.15.0-alpha4, 3.15.0-alpha5, 3.15.0-alpha6 (+1) — fixed in 3.10.0, 3.13.13, 3.14.4

How to fix

Upgrade to a fixed version: Python 3.10.0, 3.13.13, 3.14.4. Check the vendor advisory for mitigations.

References

• https://github.com/python/cpython/commit/196edfb06a7458377d4d0f4b3cd41724c1f3bd4a
• https://github.com/python/cpython/commit/24ce88b285f56ee11626cf5e472af3cd8cc7c621
• https://github.com/python/cpython/commit/642865ddf4b232da1f3b1f7abcfa3254c4bfe785
• https://github.com/python/cpython/commit/af856a7177326ac25d9f66cc6dd28b554d914fee
• https://github.com/python/cpython/commit/e0a8a6da90597a924b300debe045cdb4628ee1f3
• https://github.com/python/cpython/commit/eb0e8be3a7e11b87d198a2c3af1ed0eccf532768
• https://github.com/python/cpython/issues/145986
• https://github.com/python/cpython/pull/145987
• https://mail.python.org/archives/list/security-announce@python.org/thread/5M7CGUW3XBRY7II4DK43KF7NQQ3TPZ6R/
• http://www.openwall.com/lists/oss-security/2026/03/16/4

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