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Vulnerability record · CVE-2026-76641 · published 20 August 2026

CVE-2026-76641: Out-of-bounds read vulnerability

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.

8.7 CVSS 4.0 High EPSS 0.61% · top 53.0% CWE-125 · Out-of-bounds read Awaiting Analysis
8.7CVSS 4.0 base score
0.61%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
24 Sep 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
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

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Source: NIST National Vulnerability Database (record CVE-2026-76641), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.