Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.
History

Fri, 21 Aug 2026 13:30:00 +0000

Type Values Removed Values Added
First Time appeared Libexpat
Libexpat expat
Vendors & Products Libexpat
Libexpat expat

Thu, 20 Aug 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 20 Aug 2026 17:45:00 +0000

Type Values Removed Values Added
Description Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.
Title Expat Out-of-Bounds Read via dtdCopy
Weaknesses CWE-125
References
Metrics 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'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-08-21T11:21:12.314Z

Reserved: 2026-08-19T14:53:58.575Z

Link: CVE-2026-76641

cve-icon Vulnrichment

Updated: 2026-08-20T18:48:55.119Z

cve-icon NVD

Status : Received

Published: 2026-08-20T18:16:51.887

Modified: 2026-08-20T19:17:04.430

Link: CVE-2026-76641

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-21T13:01:21Z