CVE-2026-0877 — Protection Mechanism Failure in Mozilla Firefox

CWE-693 — Protection Mechanism Failure13 documents9 sources
Severity
8.1HIGHNVD
EPSS
0.0%
top 93.73%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Mozilla ThunderbirdMozilla Firefox
Timeline
PublishedJan 13
Latest updateFeb 2

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:NExploitability: 2.8 | Impact: 5.2

Affected Packages3 packages

▶NVDmozilla/firefox128.0 — 140.7.0+2
▶NVDmozilla/thunderbird< 140.7.0+1
▶Debianmozilla/thunderbird< 1:140.7.0esr-1~deb11u1+3

🔴Vulnerability Details

3
CVEList
Mitigation bypass in the DOM: Security component↗2026-01-13
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OSV
CVE-2026-0877: Mitigation bypass in the DOM: Security component↗2026-01-13
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GHSA
GHSA-rfgw-g9g4-685p: Mitigation bypass in the DOM: Security component↗2026-01-13
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📋Vendor Advisories

8
Ubuntu
Thunderbird vulnerabilities↗2026-02-02
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Red Hat
firefox: thunderbird: Mitigation bypass in the DOM: Security component↗2026-01-13
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Debian
CVE-2026-0877: firefox - Mitigation bypass in the DOM: Security component. This vulnerability affects Fir...↗2026
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Mozilla
Mozilla Foundation Security Advisory 2026-03: CVE-2026-0877↗
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Mozilla
Mozilla Foundation Security Advisory 2026-05: CVE-2026-0877↗
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🕵️Threat Intelligence

1
Wiz
CVE-2026-0877 Impact, Exploitability, and Mitigation Steps | Wiz↗
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CVE-2026-0877 — Protection Mechanism Failure in Mozilla | cvebase