CVE-2026-4712
Published: 24 March 2026
Summary
CVE-2026-4712 is a high-severity Exposure of Sensitive Information to an Unauthorized Actor (CWE-200) 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 30.5th 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 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-4712 is an information disclosure vulnerability (CWE-200) in the Widget: Cocoa component, affecting Mozilla Firefox, Firefox ESR, and Thunderbird. The issue enables unauthorized access to sensitive data and was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Remote attackers can exploit this vulnerability over the network with low attack complexity, requiring no privileges, no user interaction, and without altering the scope of impact. Successful exploitation results in high confidentiality impact, allowing disclosure of sensitive information from affected systems, while integrity and availability remain unaffected. The CVSS v3.1 base score is 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
Mozilla's security advisories (MFSA 2026-20, MFSA 2026-22, MFSA 2026-23, and MFSA 2026-24), along with Bugzilla entry 2017666, document the vulnerability and recommend updating to the patched versions as the primary mitigation.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14839
Vulnerability details
Information disclosure in the Widget: Cocoa component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated info disclosure (CWE-200) with high confidentiality impact directly enables collection of sensitive data from the local system on affected browsers/email clients.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates timely patching of known flaws like CVE-2026-4712, as fixed in specified Firefox and Thunderbird versions.
Enables vulnerability scanning to identify systems running vulnerable versions of Firefox, ESR, or Thunderbird affected by this information disclosure.
Requires monitoring Mozilla security advisories (e.g., MFSA 2026-20) to promptly learn of and apply patches for this CVE.
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).
Ubuntu 22.04 (1 rule)
- V-260470 Ubuntu 22.04 LTS, when booted, must require authentication upon booting into single-user and maintenance modes. via CWE-200
Ubuntu 24.04 (2 rules)
- V-270647 Ubuntu 24.04 LTS must not have the telnet package installed. via CWE-200
- V-270675 Ubuntu 24.04 LTS when booted must require authentication upon booting into single-user and maintenance modes. via CWE-200
Windows 10 (1 rule)
- V-220737 Administrative accounts must not be used with applications that access the Internet, such as web browsers, or with potential Internet sources, such as email. via CWE-200
Windows Server 2016 (1 rule)
- V-224974 Domain-created Active Directory Organizational Unit (OU) objects must have proper access control permissions. via CWE-200
Windows Server 2019 (1 rule)
- V-205743 Windows Server 2019 organization created Active Directory Organizational Unit (OU) objects must have proper access control permissions. via CWE-200
Windows Server 2022 (1 rule)
- V-254395 Windows Server 2022 organization created Active Directory Organizational Unit (OU) objects must have proper access control permissions. via CWE-200