Mozilla Firefox < 37.0.1 HTTP/2 Alt-Svc Header SSL MitM

Medium Nessus Network Monitor Plugin ID 8743


The remote host has a web browser installed that is vulnerable to a man-in-the-middle (MitM) attack.


Versions 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.


Upgrade to Firefox 37.0.1 or later.

See Also

Plugin Details

Severity: Medium

ID: 8743

Family: Web Clients

Published: 2015/04/29

Modified: 2016/03/07

Dependencies: 9131

Nessus ID: 82583, 82582

Risk Information

Risk Factor: Medium


Base Score: 4.3

Temporal Score: 3.7

Vector: CVSS2#AV:N/AC:M/Au:N/C:N/I:P/A:N

Temporal Vector: CVSS2#E:ND/RL:OF/RC:C


Base Score: 5.3

Temporal Score: 5.1


Temporal Vector: CVSS3#E:X/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:mozilla:firefox

Patch Publication Date: 2015/03/31

Vulnerability Publication Date: 2015/03/31

Reference Information

CVE: CVE-2015-0799

BID: 73905

IAVA: 2015-A-0069