Mozilla Firefox < 37.0.1 HTTP/2 Alt-Svc Header SSL MitM
Medium Nessus Network Monitor Plugin ID 8743
SynopsisThe remote host has a web browser installed that is vulnerable to a man-in-the-middle (MitM) attack.
DescriptionVersions of Mozilla Firefox earlier than 37.0.1 are affected by an error related to the HTTP/2 'Alt-Svc' header and SSL certificate verification, which allows man-in-the-middle (MitM) attacks. Specifically, this affects the script 'modules/libpref/init/all.js' as certificates are not properly validated when handling an Alt-Svc header in an HTTP/2 response. By spoofing the TLS/SSL server via a certificate that appears valid, an attacker with the ability to intercept network traffic (e.g. MiTM, DNS cache poisoning) can disclose and optionally manipulate transmitted data.
SolutionUpgrade to Firefox 37.0.1 or later.