What’s Vulnerable › Vulnerabilities

CVE-2026-76641: Expat Out-of-Bounds Read via dtdCopy

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-20 · updated 2026-10-26
• Weakness: CWE-125

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.

Affected products

• libexpat: through 2.8.3

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

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