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-2026-4702 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 49% 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-8 (Security and Privacy Engineering Principles) — 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-2026-4702 is a JIT miscompilation vulnerability in the JavaScript Engine component of Mozilla products. It affects Firefox versions prior to 149, Firefox ESR versions prior to 140.9, Thunderbird versions prior to 149, and Thunderbird versions prior to 140.9. The vulnerability, published on 2026-03-24, is classified under CWE-843 and carries a CVSS v3.1 base score of 9.8.
The vulnerability can be exploited by a remote attacker with network access, requiring low attack complexity, no privileges, and no user interaction. Exploitation results in high impacts to confidentiality, integrity, and availability (C:H/I:H/A:H) with no change in scope.
Mozilla security advisories, including MFSA2026-20, MFSA2026-22, MFSA2026-23, and MFSA2026-24, along with Bugzilla entry 2013560, confirm the issue was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. Security practitioners should prioritize updating affected products to these versions or later to mitigate the risk.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-14821
Vulnerability Data
JIT miscompilation in the JavaScript Engine 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 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.
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.