What is CVE-2026-8960?

CVE-2026-8960 is a high-severity vulnerability in Mozilla Firefox, classified under Authentication Bypass by Spoofing. CVSS score: 7.5/10. Published 2026-05-19.

How severe is CVE-2026-8960?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Mozilla Firefox

CVE-2026-8960

Spoofing issue in WebExtensions. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

EPSS: 0.000 (11.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

Affected products

Mozilla Firefox — versions 151
Mozilla Thunderbird — versions 151

Weakness classification (CWE)

CWE-290 — Authentication Bypass by Spoofing

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)
security@mozilla.org (Vendor Advisory)

Frequently asked questions

What is CVE-2026-8960?: CVE-2026-8960 is a high-severity vulnerability in Mozilla Firefox, classified under Authentication Bypass by Spoofing. CVSS score: 7.5/10. Published 2026-05-19.
How severe is CVE-2026-8960?: High severity. CVSS v3 base score is 7.5 out of 10.