CVE-2026-6760
Published: 21 April 2026
Summary
CVE-2026-6760 is a critical-severity Authentication Bypass Using an Alternate Path or Channel (CWE-288) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 17.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Mandates timely patching of known flaws like CVE-2026-6760, fixed in Firefox 150 and Thunderbird 150, to prevent exploitation of the cookie mitigation bypass.
Requires vulnerability scanning to identify systems running vulnerable Firefox or Thunderbird versions prior to 150 affected by the cookie handling bypass.
Ensures dissemination of security advisories like MFSA2026-30 and MFSA2026-33 to prompt remediation of CVE-2026-6760.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated browser vulnerability with no user interaction and high C/I/A impact directly enables client-side exploitation (T1203). Cookie handling mitigation bypass facilitates improper use of web session cookies for authentication (T1550.004).
NVD Description
Mitigation bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Deeper analysisAI
CVE-2026-6760 is a mitigation bypass vulnerability (CWE-288) in the Networking: Cookies component of Mozilla Firefox and Thunderbird. It affects versions prior to Firefox 150 and Thunderbird 150, where the issue was fixed. The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), marking it as critical due to its potential for severe impact.
Remote, unauthenticated attackers can exploit this vulnerability over the network with low attack complexity and no user interaction required. Successful exploitation enables high-impact compromise of confidentiality, integrity, and availability, allowing attackers to bypass security mitigations related to cookie handling in networking operations.
Mozilla's security advisories MFSA2026-30 and MFSA2026-33 detail the patch, which was implemented in Firefox 150 and Thunderbird 150. Additional technical information is available in Bugzilla bug 2016923.
Details
- CWE(s)