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PatchSiren cyber security CVE debrief

CVE-2026-12321 Mozilla CVE debrief

A JIT (Just-In-Time) miscompilation vulnerability was discovered in the JavaScript: WebAssembly component. This vulnerability was addressed and fixed in Firefox 152. Users are advised to update to the latest version to mitigate potential risks.

Vendor
Mozilla
Product
Firefox
CVSS
MEDIUM 5.4
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-16
Original CVE updated
2026-06-16
Advisory published
2026-06-16
Advisory updated
2026-06-16

Who should care

Users of Firefox, particularly those who use the browser for WebAssembly-related tasks or visit untrusted websites, should be aware of this vulnerability and take action to update their browser.

Technical summary

The vulnerability is caused by a JIT miscompilation in the JavaScript: WebAssembly component. This could potentially allow attackers to execute arbitrary code or cause a denial of service.

Defensive priority

High

Recommended defensive actions

  • Update Firefox to version 152 or later.

Evidence notes

The CVE record and NVD detail pages provide official information about this vulnerability. Additional details can be found in the Mozilla security advisories.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-12321 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-12321

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-12321 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-12321

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.