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SS-2015-013: X-Forwarded-Host request hostname injection

High (?)
Versions Affected:
3.1.13-rc1 and below
Versions Fixed:
Release Date:

A potential hostname injection vulnerability has been found which could allow attackers to alter url resolution.

If a request contains the X-Forwarded-Host HTTP header a website would then use its value in place of the actual HTTP hostname. In cases where caching is enabled, this could allow an attacker to potentially embed a remote url as the base_url for any site. This would then cause other visitors to the site to be redirected unknowingly.

This header is necessary for servers running behind a reverse proxy (such as nginx). Such servers are likely not vulnerable to this risk.

A fix has been merged into the default installer, although existing projects which do not run behind a reverse proxy should update their htaccess as below:

<IfModule mod_headers.c>
# Remove X-Forwarded-Host header sent as a part of any request from the web
RequestHeader unset X-Forwarded-Host

Common Vulnerability Scoring System (CVSS) Information

Thanks to Dariusz Półtorak for identifying this issue.