CVE-2026-4692
Mozilla Firefox ≤ 115.34.0
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2026-4692 is a critical-severity Improper Isolation or Compartmentalization (CWE-653) vulnerability in Mozilla Firefox. Its CVSS base score is 10.0 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Escape to Host (T1611); ranked at the 40th 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 SC-2 (Separation of System and User Functionality) and SC-3 (Security Function Isolation) — 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-2026-4692 is a sandbox escape vulnerability in the Responsive Design Mode component of Mozilla Firefox and Thunderbird. It affects Firefox versions prior to 149, Firefox ESR prior to 115.34 and 140.9, Thunderbird prior to 149, and Thunderbird prior to 140.9. Published on 2026-03-24, the flaw carries a maximum CVSS v3.1 score of 10.0 (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H), highlighting its critical severity due to network accessibility, low complexity, no prerequisites, and scope change with full triad impact.
Remote attackers require no privileges or user interaction to exploit this vulnerability over the network. Successful exploitation enables sandbox escape, potentially granting attackers high-level access to compromise confidentiality, integrity, and availability of the affected browser or email client processes.
Mozilla fixed CVE-2026-4692 in Firefox 149, Firefox ESR 115.34 and 140.9, Thunderbird 149, and Thunderbird 140.9. Security practitioners should review advisories MFSA2026-20, MFSA2026-21, MFSA2026-22, and MFSA2026-23, along with Bugzilla entry 2017643, for patch deployment guidance and additional mitigation details.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14807
Vulnerability Data
Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 8 hardening rules · 7 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Security function isolation is the canonical mechanism for protecting higher-privilege compartments.
Process isolation maintains separate execution domains so one process cannot affect another’s privilege level.
Explicit separation of user and management functionality implements the required compartmentalization.
System partitioning creates distinct domains that enforce isolation between differently privileged components.
Access enforcement directly requires approved authorizations to be applied to compartmentalized resources.
Information flow enforcement structurally prevents unauthorized mixing of data or functions across privilege boundaries.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
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.
Segregation of duties directly enforces separation of privilege levels and functions.
Network segregation is a classic technical control for isolating different privilege domains.
Secure system architecture principles explicitly call for isolation and least-privilege boundaries.
Separation of development, test and production environments is a direct application of compartmentalization.
Access control policies establish the boundaries that isolation must enforce.
Managing access rights is the operational mechanism for compartmentalizing privileges.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 9 (1 rule)
- V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-653
RHEL 9 (2 rules)
- V-258078 RHEL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-653
- V-272496 RHEL 9 must elevate the SELinux context when an administrator calls the sudo command. prevents CWE-653
Windows 10 (1 rule)
- V-220712 Only accounts responsible for the administration of a system must have Administrator rights on the system. prevents CWE-653
Windows 11 (1 rule)
- V-253269 prevents CWE-653
Windows Server 2016 (1 rule)
- V-225007 Only administrators responsible for the member server or standalone or nondomain-joined system must have Administrator rights on the system. prevents CWE-653