CVE-2026-0892: Memory safety bugs fixed in Firefox 147 and Thunderbird 147

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-13 · updated 2026-06-17
Weakness: CWE-119

Description

Memory safety bugs present in Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 147 and Thunderbird 147.

Affected products

Mozilla Firefox: before 147.0 — fixed in 147.0
Mozilla Thunderbird: before 147.0 — fixed in 147.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 147.0; Mozilla Thunderbird 147.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=1986912%2C1996718%2C1999633%2C2001081%2C2004443
https://www.mozilla.org/security/advisories/mfsa2026-01/
https://www.mozilla.org/security/advisories/mfsa2026-04/

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