# CVE-2026-76641: expat: Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption b...

CVE-2026-76641 is fixed in 4 products on 1 platform, first by expat 2.2.5-3ubuntu0.9+esm5, released August 20, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-76641
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0035
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 20, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | MozillaFirefox opensuse-leap 16.0 | 153.5.0-160000.1.1 | [OPENSUSE-SU-2026:22139-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22139-1.md) | Nov 7, 2026 |
| Linux | MozillaFirefox sles 15.6 | 153.5.0-150400.157.16.1 | [SUSE-SU-2026:4834-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4834-1.md) | Nov 7, 2026 |
| Linux | MozillaFirefox sles 15.7 | 153.5.0-150400.157.16.1 | [SUSE-SU-2026:4834-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4834-1.md) | Nov 7, 2026 |
| Linux | MozillaFirefox sles 16.0 | 153.5.0-160000.1.1 | [SUSE-SU-2026:24260-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24260-1.md) | Nov 7, 2026 |
| Linux | MozillaThunderbird sles 15.7 | 153.5.0-150400.13.9.1 | [SUSE-SU-2026:4736-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4736-1.md) | Nov 7, 2026 |
| Linux | expat Ubuntu 18.04.6 LTS (bionic) | 2.2.5-3ubuntu0.9+esm5 | [expat 2.2.5-3ubuntu0.9+esm5](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-expat-2.2.5-3ubuntu0.9-esm5.md) | Aug 20, 2026 |
| Linux | expat Ubuntu 20.04 LTS (focal) | 2.2.9-1ubuntu0.8+esm3 | [expat 2.2.9-1ubuntu0.8+esm3](https://patchblox.com/security/data/fix/linux/ubuntu-focal-expat-2.2.9-1ubuntu0.8-esm3.md) | Aug 20, 2026 |
| Linux | expat Ubuntu 22.04.1 LTS (jammy) | 2.4.7-1ubuntu0.9 | [expat 2.4.7-1ubuntu0.9](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-expat-2.4.7-1ubuntu0.9.md) | Aug 20, 2026 |
| Linux | expat Ubuntu 24.04.5 LTS (noble) | 2.6.1-2ubuntu0.6 | [expat 2.6.1-2ubuntu0.6](https://patchblox.com/security/data/fix/linux/ubuntu-noble-expat-2.6.1-2ubuntu0.6.md) | Aug 20, 2026 |
| Linux | expat Ubuntu 26.04.1 LTS (resolute) | 2.7.4-1ubuntu0.2 | [expat 2.7.4-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-expat-2.7.4-1ubuntu0.2.md) | Aug 20, 2026 |
| Linux | expat opensuse-leap 16.0 | 2.8.4-160000.1.1 | [OPENSUSE-SU-2026:21945-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21945-1.md) | Sep 24, 2026 |
| Linux | expat sles 15.6 | 2.8.5-150400.3.40.1 | [SUSE-SU-2026:4623-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4623-1.md) | Nov 7, 2026 |
| Linux | expat sles 15.7 | 2.8.5-150700.3.15.1 | [SUSE-SU-2026:4619-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4619-1.md) | Nov 7, 2026 |
| Linux | expat sles 16.0 | 2.8.4-160000.1.1 | [SUSE-SU-2026:23912-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23912-1.md) | Sep 24, 2026 |
| Linux | libexpat1 Ubuntu 18.04.6 LTS (bionic) | 2.2.5-3ubuntu0.9+esm5 | [libexpat1 2.2.5-3ubuntu0.9+esm5](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libexpat1-2.2.5-3ubuntu0.9-esm5.md) | Aug 20, 2026 |
| Linux | libexpat1 Ubuntu 20.04 LTS (focal) | 2.2.9-1ubuntu0.8+esm3 | [libexpat1 2.2.9-1ubuntu0.8+esm3](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libexpat1-2.2.9-1ubuntu0.8-esm3.md) | Aug 20, 2026 |
| Linux | libexpat1 Ubuntu 22.04.1 LTS (jammy) | 2.4.7-1ubuntu0.9 | [libexpat1 2.4.7-1ubuntu0.9](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libexpat1-2.4.7-1ubuntu0.9.md) | Aug 20, 2026 |
| Linux | libexpat1 Ubuntu 24.04.5 LTS (noble) | 2.6.1-2ubuntu0.6 | [libexpat1 2.6.1-2ubuntu0.6](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libexpat1-2.6.1-2ubuntu0.6.md) | Aug 20, 2026 |
| Linux | libexpat1 Ubuntu 26.04.1 LTS (resolute) | 2.7.4-1ubuntu0.2 | [libexpat1 2.7.4-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libexpat1-2.7.4-1ubuntu0.2.md) | Aug 20, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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