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CVE-2026-109761 Mozilla CVE debrief

Mozilla Firefox users should assess exposure to CVE-2026-109761, a use-after-free vulnerability in the JavaScript: WebAssembly component. Defenders should verify if their Firefox versions are prior to 158 and prioritize patching. This vulnerability was fixed in Firefox 158. The vulnerability affects the JavaScript: WebAssembly component of Mozilla Firefox, and its exploitation could lead to arbitrary code execution or denial of service. Therefore, defenders should assess exposure, prioritize patching to version 158 or later, and monitor for potential exploitation attempts.

Vendor
Mozilla
Product
Firefox
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-13
Original CVE updated
2026-10-13
Advisory published
2026-10-13
Advisory updated
2026-10-13

Who should care

Mozilla Firefox users and administrators should assess exposure to this vulnerability and prioritize patching to version 158 or later. Defenders should verify Firefox versions and prioritize patching to prevent potential exploitation. Successful exploitation could lead to arbitrary code execution or denial of service.

Why it matters

CVE-2026-109761 is a use-after-free vulnerability in the JavaScript: WebAssembly component of Mozilla Firefox. Defenders should assess exposure, prioritize patching to version 158 or later, and monitor for potential exploitation attempts.

  • Defenders should verify Firefox versions and prioritize patching to prevent potential exploitation.
  • Successful exploitation could lead to arbitrary code execution or denial of service.
  • Patching Firefox to version 158 or later is recommended to address the vulnerability.

Technical summary

A use-after-free vulnerability exists in the JavaScript: WebAssembly component of Mozilla Firefox. This vulnerability was fixed in Firefox 158. The vulnerability affects the JavaScript: WebAssembly component, and its exploitation could lead to arbitrary code execution or denial of service. Therefore, defenders should assess exposure, prioritize patching to version 158 or later, and monitor for potential exploitation attempts.

Defensive priority

Patching Firefox to version 158 or later is recommended to address the use-after-free vulnerability.

Recommended defensive actions

  • Patch Firefox to version 158 or later
  • Verify Firefox version is up-to-date
  • Monitor for potential exploitation attempts

Evidence notes

The CVE record and source item provide limited information about the vulnerability, but confirm that it was fixed in Firefox 158. The vulnerability is a use-after-free issue in the JavaScript: WebAssembly component of Mozilla Firefox. Defenders should verify Firefox versions and prioritize patching to prevent potential exploitation. The source details are limited, so defenders should exercise caution and verify the vulnerability's impact on their systems.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-109761 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-109761

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

  • CVE-2026-109761 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-109761

    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.