CVE-2026-6772
Published: 21 April 2026
Summary
CVE-2026-6772 is a high-severity Improper Check for Unusual or Exceptional Conditions (CWE-754) vulnerability in Mozilla Firefox. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 15.3th 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 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Mandates timely identification, reporting, and correction of software flaws like CVE-2026-6772 through patching NSS in affected Firefox and Thunderbird versions.
Enables automated scanning and monitoring to identify systems with vulnerable NSS library versions exploited by this boundary condition flaw.
Provides for receiving and distributing Mozilla security advisories (MFSA2026-*) reporting CVE-2026-6772 to initiate remediation.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability allows remote unauthenticated attackers to disclose sensitive information from the affected Mozilla client applications, directly facilitating collection of data from the local system.
NVD Description
Incorrect boundary conditions in the Libraries component in NSS. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Deeper analysisAI
CVE-2026-6772 is a vulnerability involving incorrect boundary conditions in the Libraries component of NSS (Network Security Services). It affects Mozilla products that incorporate NSS, including Firefox versions prior to 150, Firefox ESR prior to 115.35 and 140.10, Thunderbird prior to 150, and Thunderbird prior to 140.10. The issue, classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions), carries a CVSS v3.1 base score of 7.5, reflecting high severity due to its network accessibility and potential for significant impact.
The vulnerability enables exploitation by any remote, unauthenticated attacker (AV:N/AC:L/PR:N/UI:N) over the network with low complexity and no user interaction required. Successful exploitation results in high confidentiality impact (C:H), allowing attackers to disclose sensitive information without affecting integrity or availability (S:U/I:N/A:N).
Mozilla security advisories (MFSA2026-30 through MFSA2026-33) and the associated Bugzilla entry detail the patch deployment, confirming fixes in Firefox 150, Firefox ESR 115.35 and 140.10, Thunderbird 150, and Thunderbird 140.10. Security practitioners should prioritize updating to these versions to mitigate the risk.
Details
- CWE(s)