CVE-2026-2777

CRITICAL 9.8

Privilege escalation in the Messaging System component

CVSS Score

9.8

EPSS Score

0.0%

EPSS Percentile

0th

Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Vendor	mozilla
Product	firefox
Ecosystems	Browser JavaScript
Industries	Technology
Published	Feb 24, 2026
Last Updated	Apr 13, 2026

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Affected Versions

Mozilla / Firefox

All versions affected

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=2015305 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-13/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-14/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-15/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-16/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-17/

Credits

Richard Belisle