Critical severity · published Apr 21, 2026
CVE-2026-6771
Mitigation bypass in the DOM: Security component
9.8
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 24% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 150.0; 140.0 before 140.10.0 · source: NVD
TH
Thunderbird · Mozilla
140.0 before 140.10.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6771
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-6771
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2025067
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-30/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-32/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-33/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-34/
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