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PatchSiren cyber security CVE debrief

CVE-2026-12299 Mozilla CVE debrief

CVE-2026-12299 is a vulnerability in the Firefox browser, specifically affecting the JIT (Just-In-Time) compilation process in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, and Firefox ESR 115.37.

Vendor
Mozilla
Product
Firefox
CVSS
MEDIUM 5.4
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-16
Original CVE updated
2026-07-15
Advisory published
2026-06-16
Advisory updated
2026-07-15

Who should care

Users of Firefox, especially those who use the browser for sensitive activities or in high-risk environments, should be aware of this vulnerability and ensure they are running a patched version of the browser.

Technical summary

The vulnerability is related to a JIT miscompilation issue in the DOM: Core & HTML component of Firefox. This type of issue can potentially allow for arbitrary code execution or other malicious activities.

Defensive priority

High

Recommended defensive actions

  • Update Firefox to version 152 or later
  • Update Firefox ESR to version 140.12 or later
  • Update Firefox ESR to version 115.37 or later

Evidence notes

The CVE record and associated references provide evidence of the vulnerability and its fixes.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-12299 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-12299

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

  • CVE-2026-12299 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-12299

    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.