livingsocial, HTTP Header Injection, HTTP Response Splitting

CWE-113 in livingsocial.com | Vulnerability Crawler Report

Report generated by XSS.CX at Sun Jan 02 19:16:33 CST 2011.

Summary

Severity:	High
Confidence:	Certain
Host:	http://livingsocial.com
Path:	/deals/socialads_reflector

Issue detail

The value of REST URL parameter 2 is copied into the Location response header. The payload 579c7%0d%0a66bb55c34dd was submitted in the REST URL parameter 2. 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 /deals/socialads_reflector579c7%0d%0a66bb55c34dd HTTP/1.1
Host: livingsocial.com
Accept: */*
Accept-Language: en
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)
Connection: close

Response

HTTP/1.1 301 Moved Permanently
Server: nginx
Date: Sun, 02 Jan 2011 15:49:49 GMT
Content-Type: text/html
Content-Length: 178
Connection: close
Location: http://partners.livingsocial.com/deals/socialads_reflector579c7
66bb55c34dd

<html>
<head><title>301 Moved Permanently</title></head>
<body bgcolor="white">
<center><h1>301 Moved Permanently</h1></center>
<hr><center>nginx</center>
</body>
</html>