VulnerabilityModified
CVE-2026-2777
Privilege escalation in the Messaging System component.
CRITICAL 9.8EPSS 0.37%
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.37%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.37% probability · 30th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-269
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2015305Issue Tracking, Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-13/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-14/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-15/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-16/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-17/Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:3338
- https://access.redhat.com/errata/RHSA-2026:3339
- https://access.redhat.com/errata/RHSA-2026:3361
- https://access.redhat.com/errata/RHSA-2026:3491
- https://access.redhat.com/errata/RHSA-2026:3492
- https://access.redhat.com/errata/RHSA-2026:3493
- https://access.redhat.com/errata/RHSA-2026:3494
- https://access.redhat.com/errata/RHSA-2026:3495
- https://access.redhat.com/errata/RHSA-2026:3496
- https://access.redhat.com/errata/RHSA-2026:3497
- https://access.redhat.com/errata/RHSA-2026:3515
- https://access.redhat.com/errata/RHSA-2026:3516
- https://access.redhat.com/errata/RHSA-2026:3517
- https://access.redhat.com/errata/RHSA-2026:3976
- https://access.redhat.com/errata/RHSA-2026:3978
- https://access.redhat.com/errata/RHSA-2026:3979
- https://access.redhat.com/errata/RHSA-2026:3980
- https://access.redhat.com/errata/RHSA-2026:3981
- https://access.redhat.com/errata/RHSA-2026:3982
- https://access.redhat.com/errata/RHSA-2026:3983
- https://access.redhat.com/errata/RHSA-2026:3984
- https://access.redhat.com/errata/RHSA-2026:4022
- https://access.redhat.com/errata/RHSA-2026:4152
- https://access.redhat.com/errata/RHSA-2026:4260
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.