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Vulnerability · Published Feb 24, 2026 · Assigned by mozilla

CVE-2026-2777Privilege escalation in the Messaging System component

Critical 9.8

In plain English

A critical-severity privilege mismanagement in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.4%top 61.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10firefox140.8.0-2.el10_1ALSA-2026:3361
AlmaLinux:8firefox140.8.0-2.el8_10.alma.1ALSA-2026:3338
AlmaLinux:9firefox140.8.0-2.el9_7.alma.1ALSA-2026:3339
AlmaLinux:9firefox-x11140.8.0-2.el9_7.alma.1ALSA-2026:3339
AlmaLinux:10thunderbird140.8.0-2.el10_1.alma.1ALSA-2026:3517
AlmaLinux:8thunderbird140.8.0-1.el8_10.alma.1ALSA-2026:3515
AlmaLinux:9thunderbird140.8.0-1.el9_7.alma.1ALSA-2026:3516
Debian:12firefox-esr140.8.0esr-1~deb12u1DSA-6148-1
Debian:12firefox-esr140.8.0esr-1~deb12u1DEBIAN-CVE-2026-2777
Debian:13firefox-esr140.8.0esr-1~deb13u1DEBIAN-CVE-2026-2777
Debian:13firefox-esr140.8.0esr-1~deb13u1DSA-6148-1
Debian:14firefox-esr140.8.0esr-1DEBIAN-CVE-2026-2777
Debian:12thunderbird1:140.8.0esr-1~deb12u1DSA-6152-1
Debian:12thunderbird1:140.8.0esr-1~deb12u1DEBIAN-CVE-2026-2777
Debian:13thunderbird1:140.8.0esr-1~deb13u1DEBIAN-CVE-2026-2777
Debian:13thunderbird1:140.8.0esr-1~deb13u1DSA-6152-1
Debian:14thunderbird1:140.8.0esr-1DEBIAN-CVE-2026-2777
Rocky Linux:10firefox0:140.8.0-2.el10_1RLSA-2026:3361
Rocky Linux:8firefox0:140.8.0-2.el8_10RLSA-2026:3338
Rocky Linux:9firefox0:140.8.0-2.el9_7RLSA-2026:3339
Rocky Linux:10thunderbird0:140.8.0-2.el10_1RLSA-2026:3517
Rocky Linux:8thunderbird0:140.8.0-1.el8_10RLSA-2026:3515
Rocky Linux:9thunderbird0:140.8.0-1.el9_7RLSA-2026:3516
Ubuntu:22.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-2777
Ubuntu:24.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-2777
Ubuntu:24.04:LTSmozjs115no fix listedUBUNTU-CVE-2026-2777
Ubuntu:22.04:LTSmozjs78no fix listedUBUNTU-CVE-2026-2777
Ubuntu:22.04:LTSmozjs91no fix listedUBUNTU-CVE-2026-2777
Ubuntu:22.04:LTSthunderbirdno fix listedUBUNTU-CVE-2026-2777

Affected products (as reported)

VendorProductVersions
Mozilla Firefox see references
Mozilla Thunderbird see references

Weakness: CWE-269 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References