CVE-2026-6771
Published: 21 April 2026
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.
Mitigating Controls (NIST 800-53 r5)AI
Directly mandates timely patching of known flaws like CVE-2026-6771 in Firefox and Thunderbird to prevent exploitation of the DOM security mitigation bypass.
Requires receiving and acting on vendor security advisories such as Mozilla's MFSA2026-30 series that detail the vulnerability and patched versions.
Facilitates vulnerability scanning to identify systems running vulnerable Firefox or Thunderbird versions affected by the DOM security bypass.
Security SummaryAI
CVE-2026-6771 is a mitigation bypass vulnerability in the DOM Security component affecting Mozilla Firefox versions prior to 150, Firefox ESR prior to 140.10, Thunderbird prior to 150, and Thunderbird prior to 140.10. Assigned CWE-288, it carries a CVSS v3.1 base score of 9.8, indicating critical severity due to its network accessibility, low attack complexity, lack of required privileges or user interaction, and high impacts on confidentiality, integrity, and availability.
Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low complexity. Successful exploitation enables high-impact compromise of confidentiality, integrity, and availability, potentially allowing attackers to bypass security mitigations in the browser's DOM handling.
Mozilla security advisories (MFSA2026-30 through MFSA2026-34) and the associated Bugzilla entry detail the fix applied in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10, recommending immediate upgrades to patched versions for mitigation.
Details
- CWE(s)
Affected Products
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
This is a remote client-side mitigation bypass vulnerability in browser DOM security (Firefox/Thunderbird) with no privileges or user interaction required and critical CIA impact, directly enabling exploitation of client application vulnerabilities for code execution or compromise.