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Vulnerability · Published Mar 24, 2026 · Assigned by mozilla

CVE-2026-4689Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component

Critical 10.0

In plain English

A critical-severity buffer overflow 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 0.7% (higher than 53% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)10.0Critical
Exploit odds (30 days)0.7%top 47.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10firefox140.9.0-1.el10_1ALSA-2026:5931
AlmaLinux:8firefox140.9.0-1.el8_10.alma.1ALSA-2026:5932
AlmaLinux:9firefox140.9.0-1.el9_7.alma.1ALSA-2026:5930
AlmaLinux:9firefox-x11140.9.0-1.el9_7.alma.1ALSA-2026:5930
AlmaLinux:10thunderbird140.9.0-1.el10_1.alma.1ALSA-2026:6342
AlmaLinux:8thunderbird140.9.0-1.el8_10.alma.1ALSA-2026:6917
AlmaLinux:9thunderbird140.9.0-1.el9_7.alma.1ALSA-2026:6188
Debian:12firefox-esr140.9.0esr-1~deb12u1DSA-6178-1
Debian:12firefox-esr140.9.0esr-1~deb12u1DEBIAN-CVE-2026-4689
Debian:13firefox-esr140.9.0esr-1~deb13u1DEBIAN-CVE-2026-4689
Debian:13firefox-esr140.9.0esr-1~deb13u1DSA-6178-1
Debian:14firefox-esr140.9.0esr-1DEBIAN-CVE-2026-4689
Debian:12thunderbird1:140.9.0esr-1~deb12u1DSA-6179-1
Debian:12thunderbird1:140.9.0esr-1~deb12u1DEBIAN-CVE-2026-4689
Debian:13thunderbird1:140.9.0esr-1~deb13u1DEBIAN-CVE-2026-4689
Debian:13thunderbird1:140.9.0esr-1~deb13u1DSA-6179-1
Debian:14thunderbird1:140.9.0esr-1DEBIAN-CVE-2026-4689
Rocky Linux:10firefox0:140.9.0-1.el10_1RLSA-2026:5931
Rocky Linux:8firefox0:140.9.0-1.el8_10RLSA-2026:5932
Rocky Linux:9firefox0:140.9.0-1.el9_7RLSA-2026:5930
Rocky Linux:10thunderbird0:140.9.0-1.el10_1RLSA-2026:6342
Rocky Linux:8thunderbird0:140.9.0-1.el8_10RLSA-2026:6917
Rocky Linux:9thunderbird0:140.9.0-1.el9_7RLSA-2026:6188
Ubuntu:22.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-4689
Ubuntu:24.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-4689
Ubuntu:24.04:LTSmozjs115no fix listedUBUNTU-CVE-2026-4689
Ubuntu:22.04:LTSmozjs78no fix listedUBUNTU-CVE-2026-4689
Ubuntu:22.04:LTSmozjs91no fix listedUBUNTU-CVE-2026-4689
Ubuntu:22.04:LTSthunderbirdno fix listedUBUNTU-CVE-2026-4689

Affected products (as reported)

VendorProductVersions
Mozilla Firefox see references
Mozilla Thunderbird see references

Weakness: CWE-120, CWE-190 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References