What is CVE-2026-6760?

CVE-2026-6760 is a critical-severity vulnerability in Mozilla Firefox, classified under Authentication Bypass Using an Alternate Path or Channel. CVSS score: 9.8/10. Published 2026-04-21.

How severe is CVE-2026-6760?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Mozilla Firefox

CVE-2026-6760

Mitigation bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.

Published 2026-04-21 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (41.5th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 41st percentile — 41.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002

Affected products

Mozilla Firefox — versions 150
Mozilla Thunderbird — versions 150

Weakness classification (CWE)

CWE-288 — Authentication Bypass Using an Alternate Path or Channel

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
www.mozilla.org/security/advisories/mfsa2026-30/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-33/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-6760?: CVE-2026-6760 is a critical-severity vulnerability in Mozilla Firefox, classified under Authentication Bypass Using an Alternate Path or Channel. CVSS score: 9.8/10. Published 2026-04-21.
How severe is CVE-2026-6760?: Critical severity. CVSS v3 base score is 9.8 out of 10.