Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-4698 is a critical-severity Type Confusion (CWE-843) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Junk Data (T1001.001); ranked in the top 46% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — 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-2026-4698 is a JIT miscompilation vulnerability in the JavaScript Engine's JIT component, affecting Mozilla Firefox and Thunderbird. It impacts versions prior to Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The issue, published on 2026-03-24, carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) and is classified under CWE-843.
Remote attackers can exploit this vulnerability over the network with low attack complexity, requiring no privileges, user interaction, or scope change. Successful exploitation enables high-impact consequences, including unauthorized disclosure of information, modification of data, and denial of service.
Mozilla's security advisories (MFSA2026-20, MFSA2026-21, MFSA2026-22, and MFSA2026-23) and Bugzilla entry 2020906 detail the patches applied in the listed fixed versions, recommending immediate upgrades to mitigate the risk.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14813
Vulnerability Data
JIT miscompilation in the JavaScript Engine: JIT 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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V1.5.2V15.3.5
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (including fuzzing and type-aware analysis) directly finds type-confusion flaws before deployment.
Documented developer processes and standards can mandate coding patterns and compiler flags that preserve security-critical operations.
Engineering principles can require use of type-safe languages, static typing, and runtime type checks that structurally avoid allocating one type and accessing another.
Memory-protection controls limit the blast radius when a type-confusion access occurs but do not stop the flaw itself.
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.
Secure SDLC practices directly prevent type-confusion flaws via safe typing, static analysis, and code review while the control itself addresses many additional weaknesses.
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.