Apache2 - Proxy Header Remote Code Execution
Summary
DLA-553-1: apache2 - security update. Affects apache2 versions < 2.2.22-13+deb7u7. Fixed in 2.2.22-13+deb7u7. How to fix ↓
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Background
Apache2 is a widely used open-source web server software. It provides a reliable and secure platform for hosting websites and applications. The Proxy header vulnerability in Apache2 allows an attacker to manipulate the HTTP_PROXY environment variable used by CGI scripts, potentially redirecting outgoing HTTP requests to an attacker-controlled proxy.
Vulnerability Detail
The Apache2 web server uses the value of the Proxy header from HTTP requests to initialize the HTTP_PROXY environment variable for CGI scripts. This variable is then used by certain HTTP client implementations to configure the proxy for outgoing HTTP requests. By sending a malicious HTTP request with a manipulated Proxy header, a remote attacker can redirect the HTTP requests performed by a CGI script to an attacker-controlled proxy. This can lead to various security risks, including unauthorized access to sensitive information or the manipulation of outgoing requests.
How To Fix
Minimum fixed version
2.2.22-13+deb7u7
This is the first release that contains the fix.
sudo apt-get install --only-upgrade apache2Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If upgrading the apache2 package is not immediately possible, a temporary workaround is to disable the use of the Proxy header in the Apache2 server configuration. This can be done by modifying the Apache configuration file (usually located at /etc/apache2/apache2.conf or /etc/httpd/conf/httpd.conf) and adding the following line:
<IfModule mod_headers.c>
RequestHeader unset Proxy
</IfModule>
After making this change, restart the Apache2 server for the configuration to take effect. This workaround prevents the Proxy header from being used to initialize the HTTP_PROXY environment variable, mitigating the vulnerability.
Conclusion
The Proxy header vulnerability in Apache2 can be mitigated by upgrading to version 2.2.22-13+deb7u7 or later. If immediate upgrading is not possible, a temporary workaround is available by disabling the use of the Proxy header in the Apache2 server configuration. It is important to take action to protect your system from potential attacks. For further support and assistance in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for apache2 →
FAQ
This vulnerability allows a remote attacker to redirect HTTP requests performed by a CGI script to an attacker-controlled proxy. This can potentially lead to unauthorized access to sensitive information or the manipulation of outgoing requests.
The vulnerability affects Apache2 version 2.2.22-13+deb7u7 and earlier versions.
At the time of this advisory, there is no known public exploit for this vulnerability. However, it is important to apply the recommended security update or workaround to mitigate the risk.
Yes, a temporary workaround is to disable the use of the Proxy header in the Apache2 server configuration. This prevents the Proxy header from being used to initialize the HTTP_PROXY environment variable and mitigates the vulnerability.
You can find more information about this vulnerability in the Debian LTS security advisory DLA-553-1. The advisory provides details about the vulnerability, its impact, and the recommended steps to fix it.
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