Apache HTTP Server mod_proxy_ftp Wildcard Characters Cross-Site Scripting

Rapid7 Advisory R7-0033
Apache HTTP Server mod_proxy_ftp Wildcard Characters Cross-Site Scripting

Discovered: July 25, 2008
Published: August 5, 2008
Revision: 1.1
http://www.rapid7.com/advisories/R7-0033

CVE: CVE-2008-2939

1. Affected system(s):

   KNOWN VULNERABLE:
   o Apache HTTP Server 2.2.9 (and earlier 2.2.x versions)
   o Apache HTTP Server 2.0.63 (and earlier 2.0.x versions)

   NOT VULNERABLE:
   o Apache HTTP Server 1.3.x (because mod_proxy_ftp doesn't support
   wildcard
   characters)

2. Summary

   The mod_proxy_ftp module of the Apache HTTP Server is vulnerable to a
   cross-site scripting vulnerability when handling requests with wildcard
   characters (aka globbing characters).

3. Vendor status and information

   Apache HTTP Server Project
   http://httpd.apache.org

   The developers were notified of this vulnerability on July 28, 2008 via
   the private security mailing list [email protected]. They
   acknowledged it within 12 hours. On July 29, they assigned it a CVE ID.
   On August 5, the vulnerability was fixed in all SVN branches:

   o Commit to main trunk:
   http://svn.apache.org/viewvc?view=rev&revision=682868
   o Commit to 2.2 branch:
   http://svn.apache.org/viewvc?view=rev&revision=682870
   o Commit to 2.0 branch:
   http://svn.apache.org/viewvc?view=rev&revision=682871

4. Solution

   Upgrade to Apache HTTP Server 2.2.10 or 2.0.64 (as of August 6, these
   have not been released yet), or apply the patch from SVN commit
   r682868.

5. Detailed analysis

   When Apache HTTP Server is configured with proxy support
   ("ProxyRequests On" in the configuration file), and when mod_proxy_ftp
   is enabled to support FTP-over-HTTP, requests containing wildcard
   characters (asterisk, tilde, opening square bracket, etc) such as:

   GET ftp://host/*<foo> HTTP/1.0

   lead to cross-site scripting in the response returned by mod_proxy_ftp:

   […]
   <h2>Directory of <a href="/">ftp://host</a>/*<foo></h2>
   […]

   To exploit this vulnerability, 'host' must be running an FTP server,
   and the last directory component of the path (the XSS payload) must
   be composed of at least 1 wildcard character and must not contain any
   forward slashes. In practice, this last requirement is not an obstacle
   at all to develop working exploits, example:

   ftp://host/*&lt;img&#37;20src=&quot;&quot;&#37;20onerror=&quot;alert&#40;42&#41;&quot;&gt;

6. Credit

   Discovered by Marc Bevand of Rapid7.

7. Contact Information

   Rapid7, LLC
   Email: [email protected]
   Web: http://www.rapid7.com
   Phone: +1 (617) 247-1717

8. Disclaimer and Copyright

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   information constitutes acceptance AS IS, at the user's own risk.
   This information is subject to change without notice.

   This advisory Copyright (C) 2008 Rapid7, LLC. Permission is hereby
   granted to redistribute this advisory, providing that no changes are
   made and that the copyright notices and disclaimers remain intact.