CVE-2026-0877
8.1
HIGH
CVSS 3.1
EPSS 0.03%
Description
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
How to fix CVE-2026-0877
To remediate CVE-2026-0877, upgrade the affected package to a fixed version below.
- Debian/firefox-esr—upgrade to 140.7.0esr-1~deb11u1 or later
- Debian/thunderbird—upgrade to 1:140.7.0esr-1~deb11u1 or later
Is CVE-2026-0877 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 140.7.0esr-1~deb11u1
- from 0, < 1:140.7.0esr-1~deb11u1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH8.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N |