XSS in Mozilla Firefox
CVE-2026-8391
Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
EPSS: 0.001 (28.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Mozilla Firefox — versions 115.36, 150.0.3, 140.11
- Mozilla Thunderbird — versions 140.11
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org
- security@mozilla.org
- security@mozilla.org
Frequently asked questions
- What is CVE-2026-8391?
- CVE-2026-8391 is a medium-severity vulnerability in Mozilla Firefox, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2026-05-12.
- How severe is CVE-2026-8391?
- Medium severity. CVSS v3 base score is 5.3 out of 10.