CVE-2011-3656: Mozilla Firefox

Medium severity, CVSS 6.1. EPSS: 0.8% chance of exploitation in the next 30 days.

Cross-site scripting (XSS) vulnerability in Mozilla Firefox before 3.6.24 and 4.x through 7 allows remote attackers to inject arbitrary web script or HTML via vectors involving HTTP 0.9 errors, non-default ports, and content-sniffing.

Affected products

• Mozilla Firefox: before 3.6.24 (fixed in 3.6.24); from 4.0, up to and including 7.0

Published 2021-06-02. Last modified 2026-06-16.