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

High severity · published Mar 16, 2026

CVE-2026-4224

Stack overflow parsing XML with deeply nested DTD content models

7.5

CVSS

0.7%

EPSS

On KEV

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector

Network

Complexity

Low

Privileges

None

User interaction

None

Confidentiality

None

Integrity

None

Availability

High

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)0.7% · higher than 53% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

CPython · Python Software Foundation

before 3.10.21; 3.11.0 before 3.11.16; 3.12.0 before 3.12.14; 3.13.0 before 3.13.13; 3.14.0 before 3.14.4; 3.15.0a1 before 3.15.0a8 · source: vendor

Python · Python

before 3.10.0; 3.13.0 before 3.13.13; 3.14.0 before 3.14.4; 3.15.0; 3.15.0; 3.15.0; +4 more · source: NVD

Affected product

CPython

Python Software Foundation

All CPython CVEs

References

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-4224

CVE.org

https://www.cve.org/CVERecord?id=CVE-2026-4224

Patch

https://github.com/python/cpython/commit/196edfb06a7458377d4d0f4b3cd41724c1f3bd4a

github.com

https://github.com/python/cpython/commit/24ce88b285f56ee11626cf5e472af3cd8cc7c621

Patch

https://github.com/python/cpython/commit/642865ddf4b232da1f3b1f7abcfa3254c4bfe785

Patch

https://github.com/python/cpython/commit/af856a7177326ac25d9f66cc6dd28b554d914fee

Patch

https://github.com/python/cpython/commit/e0a8a6da90597a924b300debe045cdb4628ee1f3

Patch

https://github.com/python/cpython/commit/eb0e8be3a7e11b87d198a2c3af1ed0eccf532768