Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
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, ranked at the 31th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
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 Data
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
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Access enforcement directly stops unauthorized actors from obtaining sensitive information.
Information flow enforcement structurally prevents sensitive data from reaching unauthorized recipients.
Protection of information at rest prevents unauthorized exposure of stored sensitive data.
Transmission confidentiality mechanisms stop exposure of sensitive data on the wire.
Least privilege reduces the set of actors who can reach sensitive information.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
A.5.10 only requires awareness, a topic-specific acceptable-use policy stating expected behaviours/monitoring, and procedures referencing classification and other controls; per the owner's explicit rule on labelling and similar dependency-style clauses, this does not itself prevent exposure (CWE-200) unless access/DLP/etc. act on it.
Requiring the return of all physical and electronic assets plus secure deletion of organizational data from personal devices reduces the chance that sensitive information remains accessible to departing personnel.
A.5.12 only defines and communicates a classification scheme so that protection needs can be understood; per the owner's explicit rule, labeling/classification does not itself prevent exposure and requires other controls (e.g. access enforcement) to act on it.
By requiring classification labels and metadata on all information assets, the control makes it harder for sensitive data to be inadvertently exposed because downstream systems and users can recognize and enforce handling rules based on those labels.
Requiring encryption, access controls, and recipient authentication for transfers directly reduces the chance that sensitive data reaches an unauthorized observer.
Secure delivery, protected storage, and confidentiality of allocation records limit exposure of authentication material to unauthorized observers.
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.