Cyber Resilience

CVE-2026-12321

Mozilla Firefox ≤ 152.0.0

Published
16 June 2026
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 5.4
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
EPSS Score 0.0016 5th percentile
Risk Priority 41 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-12321 is a medium-severity Always-Incorrect Control Flow Implementation (CWE-670) vulnerability in Mozilla Firefox. Its CVSS base score is 5.4 (Medium).

Operationally, ranked at the 5th 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 SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — 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 152 and Thunderbird 152.

CWE(s)
CWE-670

Related Threats

CVEs Like This One

CVE-2026-16392Same product: Mozilla Firefox
CVE-2026-8971Same product: Mozilla Firefox
CVE-2026-4726Same product: Mozilla Firefox
CVE-2026-8946Same product: Mozilla Firefox
CVE-2026-12302Same product: Mozilla Firefox
CVE-2025-8030Same product: Mozilla Firefox
CVE-2026-8952Same product: Mozilla Firefox
CVE-2026-0886Same product: Mozilla Firefox
CVE-2026-6781Same product: Mozilla Firefox
CVE-2025-1017Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 152.0.0
mozilla
thunderbird
≤ 152.0.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V9.2.1

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation at post-design stages directly exercises control-flow paths and reveals mismatches between implemented and intended behavior.

SA-15 Development Process, Standards, and Tools partial match

Requiring a documented development process and supporting tools reduces the chance that incorrect control-flow logic is introduced in the first place.

SI-2 Flaw Remediation partial match

Flaw identification and remediation processes can locate and correct control-flow errors once they manifest as incorrect runtime behavior.

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 control-flow implementations via reviews, testing, and static analysis.

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.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance can detect paths that deviate from intended logic.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle processes can catch incorrect control-flow logic during design and code review.

A.8.28 Secure coding partial match
prevents

Secure coding standards and reviews directly target flawed control-flow implementations.

A.8.32 Change management partial match
prevents

Change-management gates may prevent deployment of flawed logic but do not address the coding defect itself.

References