CGI Web Server Vulnerability

Number: AV16-116
Date: 18 July 2016


The purpose of this advisory is to bring attention to multiple security advisories released concerning various web servers running Common Gateway Interface (CGI).


CCIRC is aware of multiple vulnerabilities affecting web server hosts running CGI (or allowing the execution of CGI scripts).  Exploitation of these vulnerabilities may allow an attacker to conduct man-in-the-middle (MITM) attacks and/or create denial of service conditions.

These vulnerabilities may be exploitable on any web server allowing execution of CGI and/or CGI-like scripts, with permission to use the variable “HTTP_PROXY”.

CVE References: CVE-2016-5385, CVE-2016-5386, CVE-2016-5387, CVE-2016-5388, CVE-2016-1000109, CVE-2016-1000110

Suggested Action

CCIRC recommends that system administrators identify their affected assets and potential interdependencies with their organization’s critical services, and follow their patch management process accordingly or consider applying the workarounds.


CERT/CC Vulnerability Note VU#797896 - CGI web servers assign Proxy header values from client requests to internal HTTP_PROXY environment variables:

Security Researcher Website – httpoxy:

Note to Readers

In support of Public Safety's mission to build a safe and resilient Canada, CCIRC's mandate is to help ensure the security and resilience of the vital non-federal government cyber systems that underpin Canada's national security, public safety and economic prosperity. As Canada's computer security incident response team, CCIRC is Canada's national coordination centre for the prevention and mitigation of, preparedness for, response to, and recovery from cyber incidents on non-federal government systems. It does this by providing authoritative advice and support, and coordinating information sharing and incident response.

Please note, CCIRC PGP key has recently been updated.

For general information, please contact Public Safety Canada's Public Affairs division at:

Telephone: 613-944-4875 or 1-800-830-3118
Fax: 613-998-9589

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