Cross Site Tracing (XST) enables an adversary to steal the victim's session cookie and possibly other authentication credentials transmitted in the header of the HTTP request when the victim's browser communicates to a destination system's web server.

Execution Flow

1) Explore

[Determine if HTTP Trace is enabled] Determine if HTTP Trace is enabled at the web server with which the victim has an active session

Technique

• An adversary may issue an HTTP Trace request to the target web server and observe if the response arrives with the original request in the body of the response.

2) Experiment

[Identify mechanism to launch HTTP Trace request] The adversary attempts to force the victim to issue an HTTP Trace request to the targeted application.

Technique

• The adversary probes for cross-site scripting vulnerabilities to force the victim into issuing an HTTP Trace request.

3) Exploit

[Create a malicious script that pings the web server with HTTP TRACE request] The adversary creates a malicious script that will induce the victim's browser to issue an HTTP TRACE request to the destination system's web server. The script will further intercept the response from the web server, pick up sensitive information out of it, and forward to the site controlled by the adversary.

Technique

• The adversary's malicious script circumvents the httpOnly cookie attribute that prevents from hijacking the victim's session cookie directly using document.cookie and instead leverages the HTTP TRACE to catch this information from the header of the HTTP request once it is echoed back from the web server in the body of the HTTP TRACE response.

4) Exploit

[Execute malicious HTTP Trace launching script] The adversary leverages an XSS vulnerability to force the victim to execute the malicious HTTP Trace launching script

5) Exploit

[Intercept HTTP TRACE response] The adversary's script intercepts the HTTP TRACE response from teh web server, glance sensitive information from it, and forward that information to a server controlled by the adversary.

Prerequisites

HTTP TRACE is enabled on the web server
The destination system is susceptible to XSS or an adversary can leverage some other weakness to bypass the same origin policy
Scripting is enabled in the client's browser
HTTP is used as the communication protocol between the server and the client

Skills Required

Understanding of the HTTP protocol and an ability to craft a malicious script

Resources Required

None: No specialized resources are required to execute this type of attack.

Mitigations

Administrators should disable support for HTTP TRACE at the destination's web server. Vendors should disable TRACE by default.
Patch web browser against known security origin policy bypass exploits.

Related Weaknesses

References

REF-3

Cross-Site Tracing (XST)
Jeremiah Grossman.
http://www.cgisecurity.com/whitehat-mirror/WH-WhitePaper_XST_ebook.pdf

Submission

Modifications