Citrix XenCenterWeb Multiple Vulnerabilities Jul 07 2009 02:59PM
Claudio Criscione (c criscione securenetwork it)
Secure Network - Security Research Advisory

Vuln name: Citrix XenCenterWeb Multiple Vulnerabilities
Systems affected: Citrix XenCenterWeb
Systems not affected: n/a
Severity: High
Local/Remote: Remote
Vendor URL: http://www.citrix.com
Author(s): Alberto Trivero a.trivero (at) securenetwork (dot) it [email concealed] -
Claudio Criscione c.criscione (at) securenetwork (dot) it [email concealed]
Vendor disclosure: 1/06/2009
Vendor acknowledged: 11/06/2009
Vendor patch release: n/a
Public disclosure: 06/07/2009
Advisory number: SN-2009-01
Advisory URL: http://securenetwork.it/ricerca/advisory/download/SN-2009-01.txt

*** SUMMARY ***

Citrix XenCenterWeb is a web interface for Citrix XenServer environment
Users of XenCenterWeb will be able to see a list of Virtual Machines in the
Resource Pool, perform life-cycle actions (start, shutdown, restart, etc.),
get basic information about the hosts in the Resource Pools, information about
the VMs and also connect to the console of the VMs.

Due to poor validation of some user controlled inputs, a variety of attacks
against the application and the underlying server are possible.
Cross-site scripting, cross-site request forgery, SQL injection and remote
command execution attack vectors were identified as well.

XSS and CSRF attacks can be performed on the virtual appliance itself, while
the others require the PHP parameter magic_quotes_gpc to be off on the web


(a) Cross-site Scripting (XSS) and Cross-site Request Forgery (CSRF)
With the default PHP configuration (register_globals=Off and
magic_quotes_gpc=On), both XSS and CSRF attacks can be executed.

The first XSS attack exploits the lack of sanitization in the username
parameter in edituser.php script and requires the victim to be able to access
configuration scripts:

Under the same conditions, a CSRF attack can be executed to change the
password of an arbitrary user:

Another CSRF attack can hard stop a VM of the attacker's choice:

Other XSS vulnerabilities afflict scripts which are accessible by anyone:

(b) SQL Injection
The username parameter in the login.php script is vulnerable to a Blind SQL
Injection attack.
An attacker can retrieve the whole database schema through specially crafted
Here is an example proof of concept:
https://xencenterweb.loc/login.php?username=user' UNION SELECT if(user() LIKE
'root@%', benchmark(1000000,sha1('test')), 'false')/*
Obviously, other high profile attacks can be performed through this attack

(c) Remote Command Execution
An attacker could write arbitrary data in the file
through the file /var/www/config/writeconfig.php. Due to this unsecure behavior,
arbitrary commands can be executed on the machine.
If a victim with the proper authorization follows this link:
https://xencenterweb.loc/config/writeconfig.php?pool1='; ?> <?php $cmd =
$_REQUEST['cmd']; passthru($cmd); ?> <?php $xen = '
or this URL encoded version:
an attacker can then simply execute commands on the system through the
console.php file:

*** EXPLOIT ***

Attackers may exploit these issues through a common browser as explained


No patch is currently provided by Citrix, and the application download has
been removed.
Citrix officially stated that "the tool was created to demonstrate how the SDK
could be used to create unique solutions. Customers currently using it should
assess the risks of continued use in light of your findings and, if these prove
to be unacceptable, discontinue usage".


Common web application workarounds apply, like virtual patching from a web
application firewall or similar solutions. However most of the reported issues
can be mitigated by running the application only inside the virtual appliance
or in properly configured web servers.

Secure Network would like to thank Citrix for its support during the
disclosure process.


Secure Network (www.securenetwork.it) is an information security company,
which provides consulting and training services, and engages in security
research and development.

We are committed to open, full disclosure of vulnerabilities, cooperating
whenever possible with software developers for properly handling disclosure.

This advisory is copyright 2009 Secure Network S.r.l. Permission is
hereby granted for the redistribution of this alert, provided that it is
not altered except by reformatting it, and that due credit is given. It
may not be edited in any way without the express consent of Secure Network
S.r.l. Permission is explicitly given for insertion in vulnerability
databases and similars, provided that due credit is given to Secure Network.

The information in the advisory is believed to be accurate at the time of
publishing based on currently available information. This information is
provided as-is, as a free service to the community by Secure Network
research staff. There are no warranties with regard to this information.
Secure Network does not accept any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
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If you have any comments or inquiries, or any issue with what is reported
in this advisory, please inform us as soon as possible.

E-mail: securenetwork {at} securenetwork.it
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