CVE-2026-8946: Incorrect boundary conditions in the Audio/Video: Web Codecs component

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-19 · updated 2026-10-14
Weakness: CWE-119

Description

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Affected products

Mozilla Firefox: before 115.36.0; before 151.0.0; from 140.0 before 140.11.0 — fixed in 115.36.0, 140.11.0, 151.0.0
Mozilla Thunderbird: before 140.11 — fixed in 140.11

How to fix

Upgrade to a fixed version: Mozilla Firefox 115.36.0, 140.11.0, 151.0.0; Mozilla Thunderbird 140.11. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2029070
https://www.mozilla.org/security/advisories/mfsa2026-46/
https://www.mozilla.org/security/advisories/mfsa2026-47/
https://www.mozilla.org/security/advisories/mfsa2026-48/
https://www.mozilla.org/security/advisories/mfsa2026-50/
https://www.mozilla.org/security/advisories/mfsa2026-51/
https://access.redhat.com/errata/RHSA-2026:21378
https://access.redhat.com/errata/RHSA-2026:21380
https://access.redhat.com/errata/RHSA-2026:21381
https://access.redhat.com/errata/RHSA-2026:21382
https://access.redhat.com/errata/RHSA-2026:22325
https://access.redhat.com/errata/RHSA-2026:22643

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