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9.8 Critical

CVE-2026-4702 JIT miscompilation in the JavaScript Engine component

Description

JIT miscompilation in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Affected products and versions

Product	Affected versions	Fixed in
Firefox 149	earliest → < 149	149
Firefox 140.9	earliest → < 140.9	140.9
Thunderbird 149	earliest → < 149	149
Thunderbird 140.9	earliest → < 140.9	140.9

References

bugzilla.mozilla.org bugzilla.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org
www.mozilla.org www.mozilla.org

Timeline

Published March 24, 2026
Last modified April 13, 2026

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