CVE-2026-4729criticalCWE-120 CWE-825

CVE-2026-4729: critical vulnerability in Mozilla Firefox

Memory safety bugs fixed in Firefox 149 and Thunderbird 149

Published 24 Mar 2026 · Updated 15 Jul 2026

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28Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 9.8epss 0.3%

Memory safety bugs present in Firefox 148 and Thunderbird 148. 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 149 and Thunderbird 149.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Mozilla · Firefox Mozilla · Thunderbird

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References

https://access.redhat.com/security/cve/CVE-2026-4729 https://bugzilla.mozilla.org/buglist.cgi?bug_id=1944033%2C1997282%2C2009213%2C2011412%2C2021925%2C2022034 https://bugzilla.redhat.com/show_bug.cgi?id=2450745 https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4729.json https://www.mozilla.org/security/advisories/mfsa2026-20/https://www.mozilla.org/security/advisories/mfsa2026-23/