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.

High

CVSS

7.5

Moderate

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0029

21st percentile

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

Product	Fixed in	Fix	Released
Linux
MozillaFirefox · opensuse-leap 16.0	153.5.0-160000.1.1	OPENSUSE-SU-2026:22139-1	Nov 7, 2026
MozillaFirefox · sles 15.6	153.5.0-150400.157.16.1	SUSE-SU-2026:4834-1	Nov 7, 2026
MozillaFirefox · sles 15.7	153.5.0-150400.157.16.1	SUSE-SU-2026:4834-1	Nov 7, 2026
MozillaFirefox · sles 16.0	153.5.0-160000.1.1	SUSE-SU-2026:24260-1	Nov 7, 2026
MozillaThunderbird · sles 15.7	153.5.0-150400.13.9.1	SUSE-SU-2026:4736-1	Nov 7, 2026
expat · Debian 13.5 (trixie)	2.9.0-1~deb13u1	DEBIAN-CVE-2026-76956	Sep 5, 2026
expat · Debian 14	2.8.4-1	DEBIAN-CVE-2026-76956	Sep 5, 2026
expat · opensuse-leap 16.0	2.8.4-160000.1.1	OPENSUSE-SU-2026:21945-1	Sep 24, 2026
expat · sles 15.6	2.8.5-150400.3.40.1	SUSE-SU-2026:4623-1	Nov 7, 2026
expat · sles 15.7	2.8.5-150700.3.15.1	SUSE-SU-2026:4619-1	Nov 7, 2026
expat · sles 16.0	2.8.4-160000.1.1	SUSE-SU-2026:23912-1	Sep 24, 2026

Details

Published
August 20, 2026
Weakness
Unexpected Status Code or Return Value
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-76956

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