Difference between revisions of "HTTP Response Splitting"

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(Related Vulnerabilities)
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==Related [[Vulnerabilities]]==
==Related [[Vulnerabilities]]==
[[:Category:Input Validation Vulnerability]]
* [[:Category:Input Validation Vulnerability]]
==Related [[Controls]]==
==Related [[Controls]]==

Revision as of 06:31, 2 July 2008


Last revision: 07/2/2008


HTTP response splitting vulnerabilities occur when:

  • Data enters a web application through an untrusted source, most frequently an HTTP request.

As with many software security vulnerabilities, HTTP response splitting is a means to an end, not an end in itself. At its root, the vulnerability is straightforward: an attacker passes malicious data to a vulnerable application, and the application includes the data in an HTTP response header.

To mount a successful exploit, the application must allow input that contains CR (carriage return, also given by %0d or \r) and LF (line feed, also given by %0a or \n)characters into the header. These characters not only give attackers control of the remaining headers and body of the response the application intends to send, but also allows them to create additional responses entirely under their control.


The following code segment reads the name of the author of a weblog entry, author, from an HTTP request and sets it in a cookie header of an HTTP response.

	String author = request.getParameter(AUTHOR_PARAM);
	Cookie cookie = new Cookie("author", author);

Assuming a string consisting of standard alpha-numeric characters, such as "Jane Smith", is submitted in the request the HTTP response including this cookie might take the following form:

	HTTP/1.1 200 OK
	Set-Cookie: author=Jane Smith

However, because the value of the cookie is formed of unvalidated user input the response will only maintain this form if the value submitted for AUTHOR_PARAM does not contain any CR and LF characters. If an attacker submits a malicious string, such as "Wiley Hacker\r\nHTTP/1.1 200 OK\r\n...", then the HTTP response would be split into two responses of the following form:

	HTTP/1.1 200 OK
	Set-Cookie: author=Wiley Hacker
	HTTP/1.1 200 OK

Clearly, the second response is completely controlled by the attacker and can be constructed with any header and body content desired. The ability of attacker to construct arbitrary HTTP responses permits a variety of resulting attacks, including: cross-user defacement, web and browser cache poisoning, cross-site scripting and page hijacking.

Related Threat Agents

Related Attacks

Related Vulnerabilities

Related Controls

Category:Input Validation


  • Watchfire Whitepaper: HTTP Response Splitting, Web Cache Poisoning Attacks, and Related Topics Whitepaper[1]


This article includes content generously donated to OWASP by Fortify.JPG.