CVE-2026-76641: Libexpat

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Libexpat Libexpat: up to and including 2.8.3

Published 2026-08-20. Last modified 2026-09-24.