CVE-2026-4689
10.0
CRITICAL
CVSS 3.1
EPSS 0.03%
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.
How to fix CVE-2026-4689
To remediate CVE-2026-4689, upgrade the affected package to a fixed version below.
- Debian/firefox-esr—upgrade to 140.9.0esr-1~deb11u1 or later
- Debian/thunderbird—upgrade to 1:140.9.0esr-1~deb11u1 or later
Is CVE-2026-4689 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 140.9.0esr-1~deb11u1
- from 0, < 1:140.9.0esr-1~deb11u1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | CRITICAL10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |