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CVE-2026-8389 Mozilla CVE debrief

CVE-2026-8389 is a HIGH severity vulnerability in Mozilla Firefox, with a CVSS score of 8.8. The vulnerability is caused by a JIT miscompilation in the JavaScript Engine. This issue was fixed in Firefox 150.0.3. The vulnerability was published on [cvePublishedAt](https://www.cve.org/CVERecord?id=CVE-2026-8389) and last modified on [cveModifiedAt](https://nvd.nist.gov/vuln/detail/CVE-2026-8389).

Vendor
Mozilla
Product
Firefox
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-12
Original CVE updated
2026-07-15
Advisory published
2026-05-12
Advisory updated
2026-07-15

Who should care

Users of Mozilla Firefox, particularly those who use the browser for sensitive activities, should be aware of this vulnerability and ensure they are running Firefox 150.0.3 or later.

Technical summary

The vulnerability is caused by a JIT miscompilation in the JavaScript Engine. This issue was fixed in Firefox 150.0.3. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Defensive priority

HIGH

Recommended defensive actions

  • Update to Firefox 150.0.3 or later

Evidence notes

The vulnerability was published on [cvePublishedAt](resourceLinkAnnotations:cve-org) and last modified on [cveModifiedAt](resourceLinkAnnotations:nvd).

Sources and references

Verified primary and authoritative sources

  • CVE-2026-8389 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-8389

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

  • CVE-2026-8389 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-8389

    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.