Name: CVE-2026-76641: Out-of-bounds Read
Creator: Rapid7
Published: 2026-08-20T00:00:00.000Z
License: https://www.rapid7.com/legal/website-terms-of-use/
Keywords: CVE, CVE-2026-76641, CWE-125, CVSS 7.5, EPSS 0.00353

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 Details

CVSS 4.0 Base Score: 8.7 (HIGH)
CVSS 4.0 Vector: (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:X/V:X/RE:X/U:X)
CVSS 3.1 Base Score: 7.5
CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Covered by Rapid7

Product	Vendor Advisory	Solution File	Added	Published
Alpine Linux	—	Upgrade expat	Sep 1, 2026	Aug 20, 2026
Freebsd	—	Upgrade expat2	Sep 2, 2026	Sep 1, 2026
Ibm Aix	—	Apply the fix or workaround for python_advisory21	Sep 15, 2026	Sep 15, 2026
Redhat_linux	—	No solution exists	Sep 28, 2026	Aug 20, 2026
Ubuntu	—	Upgrade libexpat1 (Ubuntu Pro)Upgrade expatUpgrade lib64expat1-dev (Ubuntu Pro)Upgrade libexpat1Upgrade libexpat1-dev (Ubuntu Pro)Upgrade expat (Ubuntu Pro)Upgrade libexpat1-devUpgrade lib64expat1 (Ubuntu Pro)	Sep 24, 2026	Aug 20, 2026

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CVSS Details

Covered by Rapid7

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