CVE-2025-11719: Use-after-free caused by the native messaging web extension API on Windows

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-14 · updated 2026-10-18
Weakness: CWE-416

Description

Starting in Thunderbird 143, the use of the native messaging API by web extensions on Windows could lead to crashes caused by use-after-free memory corruption. This vulnerability was fixed in Firefox 144 and Thunderbird 144.

Affected products

Mozilla Firefox: from 143.0 before 144.0 — fixed in 144.0
Mozilla Thunderbird: from 143.0 before 144.0 — fixed in 144.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 144.0; Mozilla Thunderbird 144.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1991950
https://www.mozilla.org/security/advisories/mfsa2025-81/
https://www.mozilla.org/security/advisories/mfsa2025-84/

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