# CVE-2026-76956: In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads to insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of service via crafted XML content.

CVE-2026-76956 is fixed in 3 products on 1 platform, first by DEBIAN-CVE-2026-76956, released September 5, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-76956
- Priority: High
- CVSS: 7.5 (Moderate)
- EPSS: 0.0029
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 20, 2026
- Weakness: Unexpected Status Code or Return Value
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-76956

## Description

In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads to insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of service via crafted XML content.

## 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 Debian 13.5 (trixie) | 2.9.0-1~deb13u1 | [DEBIAN-CVE-2026-76956](https://patchblox.com/security/data/fix/linux/debian-cve-2026-76956.md) | Sep 5, 2026 |
| Linux | expat Debian 14 | 2.8.4-1 | [DEBIAN-CVE-2026-76956](https://patchblox.com/security/data/fix/linux/debian-cve-2026-76956.md) | Sep 5, 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 |

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Data as of 2026-11-09T07:25:28Z 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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