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 18.5th 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).
Deeper analysis
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.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24113
Vulnerability details
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.
- CWE(s)
Related Threats
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.
CVEs Like This One
Affected Assets
Mitigating Controls
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.
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 (3 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. via CWE-754
- V-248573 The OL 8 file integrity tool must notify the system administrator (SA) when changes to the baseline configuration or anomalies in the operation of any security functions are discovered within an organizationally defined frequency. via CWE-754
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. via CWE-754
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. via CWE-754