CVE-2026-56412

libexpat: libexpat: Use-after-free vulnerability due to improper handling of XML CDATA sections

Published Jun 21, 2026 CVSS 3.1 · 4.9 Medium EPSS < 1% KEV · Not listed
Description
libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4765-1 expat security update
Debian DSA Debian DSA DSA-6404-1 expat security update
Ubuntu USN Ubuntu USN USN-8790-1 Expat vulnerabilities
History
Type Values Removed Values Added
Title Use-After-Free Vulnerability in libexpat Due to Missing Depth Tracking libexpat: libexpat: Use-after-free vulnerability due to improper handling of XML CDATA sections
Weaknesses CWE-825
References
Metrics threat_severity

None

threat_severity

Moderate

Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Title Use-After-Free Vulnerability in libexpat Due to Missing Depth Tracking
Type Values Removed Values Added
Description libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219.
First Time appeared Libexpat Project
Libexpat Project libexpat
Weaknesses CWE-416
CPEs cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
Vendors & Products Libexpat Project
Libexpat Project libexpat
References
Metrics cvssV3_1

{'score': 4.9, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Nov 10, 2026, 12:48 PM
Reserved
Jun 21, 2026, 3:58 PM
Status
Modified
Published
Jun 21, 2026, 5:16 PM
Modified
Nov 10, 2026, 1:19 PM
Severity
Moderate
Public date
Jun 21, 2026, 3:58 PM