BugTraq
IE UXSS (Universal XSS in IE, was Re: Microsoft Internet Information Services UTF-7 XSS Vulnerability [MS06-053]) Oct 02 2006 12:36PM
Paul Szabo (psz maths usyd edu au) (1 replies)
Eiji James Yoshida wrote in
http://lists.grok.org.uk/pipermail/full-disclosure/2006-October/049784.h
tml
:

> If 'Encoding' is set to 'Auto Select', and Internet Explorer finds a UTF-7
> string in the response's body, it will set the charset encoding to UTF-7
> automatically ...
> Proof of concept:
> http://MaliciousSite/+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-...

I know that Apache servers return

The requested URL /xyz was not found on this server.

when fetching http://apache.svr/xyz . Trouble is that IE shows a "custom"
error message, ignoring the error body. Pondering, see that

http://en.wikipedia.org/wiki/HTTP_404

says:

> ... Internet Explorer will not display these pages, however, unless they
> are larger than 512 bytes. ...

This provides UXSS (Universal Cross-Site Scripting):

http://apache.svr/+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-/ZZZ...

(with a couple of hundred Zs) will do what we want. Works for https also:

https://apache.svr/+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-/ZZZ...

Can steal any Apache server (http or https) cookies. I do not have easy
access to ISS servers to test whether similar attacks would work there.

Will Apache fix (carefully escape) the error message? Will MS fix IE to
not be so over-friendly?

In the meantime, do not use IE to do anything "private" like banking...

Cheers,

Paul Szabo psz (at) maths.usyd.edu (dot) au [email concealed] http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics University of Sydney Australia

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