CVE-2026-76641

HIGH 7.5

Expat Out-of-Bounds Read via dtdCopy

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-125
Vendor	libexpat
Product	libexpat
Published	Aug 20, 2026
Last Updated	Aug 20, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

libexpat / libexpat

0 ≤ 2.8.3

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/libexpat/libexpat/pull/1331 github.com: https://github.com/libexpat/libexpat/commit/98599f6dcc2b460410881fe420f5f55d6bec63bf vulncheck.com: https://www.vulncheck.com/advisories/expat-out-of-bounds-read-via-dtdcopy

Credits

ZeyouLiu (@liuzeyouzeyou) ZeyouLiu (@liuzeyouzeyou)