What’s Vulnerable › Vulnerabilities

CVE-2026-6771: Mitigation bypass in the DOM: Security component

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-21 · updated 2026-10-26
• Weakness: CWE-288

Description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Affected products

• Mozilla Firefox: before 150.0; from 140.0 before 140.10.0 — fixed in 150.0, 140.10.0
• Mozilla Thunderbird: from 140.0 before 140.10.0 — fixed in 140.10.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 150.0, 140.10.0; Mozilla Thunderbird 140.10.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2025067
• https://www.mozilla.org/security/advisories/mfsa2026-30/
• https://www.mozilla.org/security/advisories/mfsa2026-32/
• https://www.mozilla.org/security/advisories/mfsa2026-33/
• https://www.mozilla.org/security/advisories/mfsa2026-34/

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