Httpoxy - Proxy Header Misuse

Reference

Plugin Id: 10107 | CWE: 20

Remediation

To remediate the Httpoxy vulnerability, the following steps can be taken:

Update affected software: Ensure that all software and libraries used in the web application are updated to the latest versions. This includes the web server, programming language, and any third-party libraries.
Disable HTTP Proxy header: Configure the web server or application to ignore or remove the HTTP Proxy header from incoming requests. This can be done by modifying the server configuration file or application code.

Example configuration for Apache web server:
```
RequestHeader unset Proxy
```
Example configuration for Nginx web server:
```
proxy_set_header Proxy "";
```
Implement input validation: Validate and sanitize all user-supplied input to prevent malicious Proxy headers from being processed by the application. This can be done by using input validation and output encoding techniques.

Example code in PHP:
```
$proxyHeader = $_SERVER['HTTP_PROXY'];
if (!empty($proxyHeader)) {
    // Handle the Proxy header securely
}
```
Monitor and log outgoing connections: Implement logging and monitoring mechanisms to detect any suspicious outgoing connections initiated by the web application. This can help identify any unauthorized proxying attempts.

About

Httpoxy is a vulnerability that occurs when a server initiates a proxied request using the proxy specified in the HTTP Proxy header of the incoming request. This vulnerability is commonly found in CGI or CGI-like environments. Attackers can exploit this vulnerability to proxy outgoing HTTP requests made by the web application, direct the server to open connections to arbitrary addresses and ports, or tie up server resources by forcing the vulnerable software to use a malicious proxy.

Risks

The Httpoxy vulnerability poses several risks to the affected web application:

Proxying outgoing requests: Attackers can use the vulnerability to proxy outgoing HTTP requests made by the web application. This can allow them to intercept sensitive information, modify the requests, or perform other malicious activities.
Unauthorized outgoing connections: By exploiting Httpoxy, attackers can direct the server to open outgoing connections to an address and port of their choosing. This can be used to establish unauthorized communication channels or launch attacks against other systems.
Resource exhaustion: Attackers can force the vulnerable software to use a malicious proxy, which can tie up server resources. This can lead to degraded performance, denial of service, or other disruptions to the web application’s functionality.