[27991] in bugtraq
acFreeProxy Cross-Site Scripting Vulnerability/Possible DoS
daemon@ATHENA.MIT.EDU (Matthew Murphy)
Mon Nov 25 18:17:58 2002
Message-ID: <000501c29365$c61f1160$e62d1c41@kc.rr.com>
From: "Matthew Murphy" <mattmurphy@kc.rr.com>
To: "SecurITeam News" <news@securiteam.com>,
"BugTraq" <bugtraq@securityfocus.com>,
"VulnWatch" <vulnwatch@vulnwatch.org>,
"Vuln-Dev" <vuln-dev@securityfocus.com>
Date: Sat, 23 Nov 2002 21:01:23 -0600
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Product Information
acFreeProxy (aka "acfp") is an HTTP/1.x proxy for Microsoft Windows
environments. It offers caching, and several other features, and has a
plug-in format designed for extensibility. A flaw in the product may allow
attackers to execute content across domains.
Description
The proxy server may generate an error message if given a host that it
cannot reach, or some other exceptional condition. The error page generated
during this process does not have any input validation, and is vulnerable to
cross-site scripting. This allows an attacker to inject code as *any site*
the victim can visit, because this problem is in the proxy, and not a
specific site.
Impact
This vulnerability is significantly more dangerous than any site-specific
flaw, as it can be exploited to read content from any domain, instead of the
limited scope of a typical cross-site scripting flaw, where the site that is
flawed is the only site that can be impacted.
Exploit
http://www.hotmail.com:41997/%3CSCRIPT%3Ealert%28document%3EURL%29%3C/SCRIPT
%3E/
If a vulnerable proxy is being run, script execution begins.
I've also found bizarre crash behavior within acfp. When it accesses
www.hotmail.com it crashes for some reason that I have yet to isolate. I
believe that this may have something to do with empty entities in responses.
Any ideas?
