XSS in Mozilla Firefox
CVE-2020-26958
Firefox did not block execution of scripts with incorrect MIME types when the response was intercepted and cached through a ServiceWorker. This could lead to a cross-site script inclusion vulnerability, or a Content Security Policy bypass. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.013 (67.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Mozilla Firefox — versions < 83
- Mozilla Firefox Esr — versions < 78.5
- Mozilla Firefox_esr
- Mozilla Thunderbird — versions < 78.5
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required, x_refsource_MISC, Issue Tracking, Vendor Advisory)
- security@mozilla.org (x_refsource_CONFIRM, Vendor Advisory)
- security@mozilla.org (x_refsource_CONFIRM, Vendor Advisory)
- security@mozilla.org (x_refsource_CONFIRM, Vendor Advisory)
Frequently asked questions
- What is CVE-2020-26958?
- CVE-2020-26958 is a medium-severity vulnerability in Mozilla Firefox, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2020-12-09.
- How severe is CVE-2020-26958?
- Medium severity. CVSS v3 base score is 6.1 out of 10.