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 19.7th 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).
Deeper analysis
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.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24101
Vulnerability details
Mitigation bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
- CWE(s)
Related Threats
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).
CVEs Like This One
Affected Assets
Mitigating Controls
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.
Hardening callouts derived
Configuration rules from DISA STIG baselines that reduce the attack surface for weaknesses of the type cited by this CVE. Derived transitively via CVE→CWE→STIG over `controls_xwalks` (authoritative rows only).
Oracle Linux 8 (2 rules)
- V-248598 There must be no ".shosts" files on the OL 8 operating system. via CWE-288
- V-248827 OL 8 must not have the rsh-server package installed. via CWE-288
Oracle Linux 9 (2 rules)
- V-271757 OL 9 file systems must not contain shosts.equiv files. via CWE-288
- V-271758 OL 9 file systems must not contain .shosts files. via CWE-288
RHEL 7 (3 rules)
- V-204424 The Red Hat Enterprise Linux operating system must not allow accounts configured with blank or null passwords. via CWE-288
- V-204440 Red Hat Enterprise Linux operating systems version 7.2 or newer using Unified Extensible Firmware Interface (UEFI) must require authentication upon booting into single-user and maintenance modes. via CWE-288
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. via CWE-288