HTTP Header Injection | Information with respect to ad.uk.doubleclick.net

The DORK Report

Summary

Severity:	High
Confidence:	Certain
Host:	http://ad.uk.doubleclick.net
Path:	/adj/fno.com/home

Issue detail

The value of REST URL parameter 1 is copied into the Location response header. The payload 2dcae%0d%0a334a66a2653 was submitted in the REST URL parameter 1. This caused a response containing an injected HTTP header.

Issue background

HTTP header injection vulnerabilities arise when user-supplied data is copied into a response header in an unsafe way. If an attacker can inject newline characters into the header, then they can inject new HTTP headers and also, by injecting an empty line, break out of the headers into the message body and write arbitrary content into the application's response.

Various kinds of attack can be delivered via HTTP header injection vulnerabilities. Any attack that can be delivered via cross-site scripting can usually be delivered via header injection, because the attacker can construct a request which causes arbitrary JavaScript to appear within the response body. Further, it is sometimes possible to leverage header injection vulnerabilities to poison the cache of any proxy server via which users access the application. Here, an attacker sends a crafted request which results in a "split" response containing arbitrary content. If the proxy server can be manipulated to associate the injected response with another URL used within the application, then the attacker can perform a "stored" attack against this URL which will compromise other users who request that URL in future.

Issue remediation

If possible, applications should avoid copying user-controllable data into HTTP response headers. If this is unavoidable, then the data should be strictly validated to prevent header injection attacks. In most situations, it will be appropriate to allow only short alphanumeric strings to be copied into headers, and any other input should be rejected. At a minimum, input containing any characters with ASCII codes less than 0x20 should be rejected.

Request

GET /2dcae%0d%0a334a66a2653/fno.com/home HTTP/1.1
Host: ad.uk.doubleclick.net
Accept: */*
Accept-Language: en
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)
Connection: close

Response

HTTP/1.1 302 Moved Temporarily
Content-Type: text/html
Content-Length: 36
Location: http://static.2mdn.net/2dcae
334a66a2653/fno.com/home:
Date: Sat, 06 Nov 2010 16:21:54 GMT
Server: GFE/2.0
Connection: close

<h1>Error 302 Moved Temporarily</h1>

Report generated by Hoyt LLC at Sat Nov 06 13:42:48 CDT 2010.