CVE-2026-117966 in Firefox

Summary

by MITRE • 10/27/2026

Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.

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• Responsible: Mozilla
• Reservation: 10/27/2026
• Disclosure: 10/27/2026
• Moderation: accepted
• Entry: VDB-427339
• CPE: 20261027
• CWE: CWE-653 (confirmed)
• CVSS: 6.3 (VulDB)
• EPSS: 0.00000
• KEV: no
• Activities: very low
• Sector: Telecommunication, Homeoffice, ...

Sources

• MITRE: https://www.cve.org/CVERecord?id=CVE-2026-117966
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-117966
• CVE Details: https://www.cvedetails.com/cve/CVE-2026-117966/