CVE-2026-76641

EUVD-2026-63493

20.08.2026, 18:16

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.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
VulnCheck	CNA	7.5 HIGH	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Base Score

CVSS 3.x

EPSS Score

Percentile: Unknown

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
libexpat_project	libexpat	𝑥 ≤ 2.8.3	CNA

Debian Releases

Debian Product

Codename

expat

bookworm	2.5.0-1+deb12u2 fixed
bookworm (security)	2.5.0-1+deb12u1 fixed
bullseye	2.2.10-2+deb11u5 fixed
bullseye (security)	2.2.10-2+deb11u7 fixed
forky	2.8.3-1 fixed
sid	2.8.3-1 fixed
trixie	2.7.1-2 fixed
trixie (security)	2.8.3-1~deb13u1 fixed

Common Weakness Enumeration

CWE-125 - Out-of-bounds Read
The software reads data past the end, or before the beginning, of the intended buffer.

References

https://github.com/libexpat/libexpat/commit/98599f6dcc2b460410881fe420f5f55d6bec63bf

https://github.com/libexpat/libexpat/pull/1331

https://www.vulncheck.com/advisories/expat-out-of-bounds-read-via-dtdcopy