---
id: CVE-2026-76641
title: >-
  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
summary: >-
  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…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-125
published: '2026-08-20'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T20:02:50.260'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-76641'
references:
  - url: >-
      https://github.com/libexpat/libexpat/commit/98599f6dcc2b460410881fe420f5f55d6bec63bf
    label: disclosure@vulncheck.com
  - url: 'https://github.com/libexpat/libexpat/pull/1331'
    label: disclosure@vulncheck.com
  - url: 'https://www.vulncheck.com/advisories/expat-out-of-bounds-read-via-dtdcopy'
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00609
epssPercentile: 0.4686
ingestedAt: '2026-09-24T20:51:40.212Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.