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CVE-2026-12309 Mozilla CVE debrief

A memory safety bug was fixed in Firefox 152. This vulnerability was fixed in Firefox 152 and Firefox ESR 140.12. The bug was reported to Mozilla via Bugzilla and addressed in security advisories.

Vendor
Mozilla
Product
Firefox
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-16
Original CVE updated
2026-06-18
Advisory published
2026-06-16
Advisory updated
2026-06-18

Who should care

Users of Firefox 151 or earlier and Firefox ESR 140.11 or earlier should update to Firefox 152 or Firefox ESR 140.12 to address this vulnerability.

Technical summary

A memory safety bug was fixed in Firefox 152. This vulnerability could potentially allow an attacker to execute arbitrary code or cause a denial-of-service condition.

Defensive priority

High

Recommended defensive actions

  • Update to Firefox 152 or Firefox ESR 140.12

Evidence notes

The CVE record and NVD detail pages provide information on this vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-12309 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-12309

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

  • CVE-2026-12309 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-12309

    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.