CVE-2026-0877

HIGH

Firefox <147- Thunderbird <140.7 - Mitigation Bypass

Title source: llm

Description

Mitigation bypass in the DOM: Security component. This vulnerability affects Firefox < 147, Firefox ESR < 115.32, Firefox ESR < 140.7, Thunderbird < 147, and Thunderbird < 140.7.

References (6)

[Permissions Required] https://bugzilla.mozilla.org/show_bug.cgi?id=1999257

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2026-01/

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2026-02/

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2026-03/

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2026-04/

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2026-05/

Scores

CVSS v3 8.1

EPSS 0.0002

EPSS Percentile 5.1%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Classification

CWE

CWE-693

Status published

Affected Products (4)

mozilla/firefox < 115.32.0

mozilla/firefox < 147.0

mozilla/thunderbird < 140.7.0

mozilla/thunderbird < 147.0

Timeline

Published Jan 13, 2026

Tracked Since Feb 18, 2026