CVE-2026-74938

CRITICAL 9.1CVE-2026-74938 · Published 18/08/2026 · updated 19/08/2026

In short

CVE-2026-74938 is a CRITICAL (CVSS 9.1) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.44%, higher than 38.4% of all vulnerabilities.
Fix: update to 153.1.0, 154.0.0, 154.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`< 153.1.0< 154.0.0`	`153.1.0154.0.0`
thunderbird mozilla	`< 153.1.0< 154.0`	`153.1.0154.0`

Description

Mitigation bypass in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

References

bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2026-74 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-77 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-78 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-80 · Vendor Advisory

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Package

Affected versions

Patched versions

firefox

mozilla

< 153.1.0< 154.0.0

153.1.0154.0.0

thunderbird

mozilla

< 153.1.0< 154.0

153.1.0154.0

More vulnerabilities in firefox

See all →