CVE-2026-4224

Stack overflow parsing XML with deeply nested DTD content models

Published Mar 16, 2026 CVSS 4.0 · 6 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4583-1 python3.9 security update
Ubuntu USN Ubuntu USN USN-8509-1 Python vulnerabilities
History
Type Values Removed Values Added
First Time appeared Python python
CPEs cpe:2.3:a:python:python:*:*:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha1:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha2:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha3:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha4:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha5:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha6:*:*:*:*:*:*
cpe:2.3:a:python:python:3.15.0:alpha7:*:*:*:*:*:*
Vendors & Products Python python
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
First Time appeared Python
Python cpython
Vendors & Products Python
Python cpython
Type Values Removed Values Added
Weaknesses CWE-805
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Weaknesses CWE-674
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Stack overflow parsing XML with deeply nested DTD content models
References
Metrics cvssV4_0

{'score': 6, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
PSF
Published
Updated
Aug 13, 2026, 12:27 AM
Reserved
Mar 15, 2026, 6:10 PM
Status
Modified
Published
Mar 16, 2026, 6:16 PM
Modified
Aug 13, 2026, 1:16 AM
Severity
Moderate
Public date
Mar 16, 2026, 5:52 PM