Cyber Resilience

CVE-2026-16363

Memory Safety in Mozilla Firefox ≤ 140.13.0

Published
21 July 2026
Modified
24 July 2026
Patch / advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0044 36th percentile
Risk Priority 70 floored blend · peak EPSS

Summary

CVE-2026-16363 is a critical-severity Incorrect Calculation (CWE-682) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 36th 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 SI-2 (Flaw Remediation) and CM-7 (Least Functionality) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
Why these techniques?

JIT miscompilation in browser WebAssembly enables remote code execution via crafted JS/WASM content in client applications (e.g., malicious webpage).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-16410Same product: Mozilla Firefox
CVE-2024-7652Same product: Mozilla Firefox
CVE-2025-9187Same product: Mozilla Firefox
CVE-2026-7322Same product: Mozilla Firefox
CVE-2026-2796Same product: Mozilla Firefox
CVE-2026-12312Same product: Mozilla Firefox
CVE-2026-8973Same product: Mozilla Firefox
CVE-2025-9185Same product: Mozilla Firefox
CVE-2026-7324Same product: Mozilla Firefox
CVE-2026-16350Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 140.13.0 · ≤ 153.0.0
mozilla
thunderbird
≤ 140.13.0 · 141.0 — 153.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SI-2 Flaw Remediation
  • CM-7 Least Functionality
Detect
Catch it (NIST detect / respond)
  • SI-7 Software, Firmware, and Information Integrity
Harden
Shrink the surface (DISA STIG)

Validate
Prove the fix (OWASP ASVS)
  • V15.2.2
  • V1.5.2
  • V3.2.3
  • V15.3.5

Mitigating Controls (NIST 800-53 r5) AI

prevent

Directly requires timely application of the vendor patch that corrects the JIT miscompilation in WebAssembly.

prevent

Allows disabling or restricting the WebAssembly/JIT feature that contains the type-confusion flaw.

detect

Verifies integrity of browser binaries and JIT-generated code to detect post-exploitation tampering from the miscompilation.

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.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly prevent incorrect calculations via reviews, testing, and verification in security-critical code.

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.

detects

Security testing in development and acceptance can detect calculation flaws before deployment.

prevents

Secure development lifecycle mandates verification steps that catch incorrect calculations before they reach production.

prevents

Application security requirements can explicitly call for numeric accuracy and bounds checking.

degrades

Secure architecture principles include input validation and safe arithmetic design that reduce calculation errors.

prevents

Secure coding standards directly prohibit unsafe arithmetic and require defensive checks against incorrect results.

References