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Corsaire Security Advisory - VMware ESX Server Password Cross Site Request Forgery issue Jul 31 2006 12:53PM
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-- Corsaire Security Advisory --

Title: VMware ESX Server Password Cross Site Request Forgery issue
Date: 14.11.05
Application: VMware ESX prior to 2.5.3 upgrade patch 2
VMware ESX prior to 2.1.3 upgrade patch 1
VMware ESX prior to 2.0.2 upgrade patch 1
Environment: VMware ESX
Author: Stephen de Vries [stephen.de.vries (at) corsaire (dot) com [email concealed]]
Audience: General distribution
Reference: c051114-001

-- Scope --

The aim of this document is to clearly define an issue that exists with
the VMware ESX Server product [1] that will allow a remote attacker to
set arbitrary passwords for users under certain conditions.

-- History --

Discovered: 11.11.05 (Stephen de Vries)
Vendor notified via client: 15.11.05
Vendor notified directly: 19.05.06
Document released: 31.07.06

-- Overview --

VMware ESX Server is described [1] as virtual infrastructure software
for partitioning, consolidating and managing servers in mission-critical
environments.

The software provides a virtualization layer that allows multiple x86
based operating systems to run on the same hardware concurrently. The
ESX Server product differs from other VMware products in that it does
not require a "host" operating system to be provided by the user.
Instead, it uses a custom x86 kernel as the host, along with a
customised Linux operating system as a "console O/S".

VMware ESX Server includes a number of network services and a web
application, called the "VMware Management Interface" that can be used
to perform remote administration of the system.

-- Analysis --

One of the functions provided by the Management Interface is allowing
users to change their passwords, and in the case of the root user, to
change other users' passwords. Through an HTML form, the user is
requested to enter and confirm their new password, but they are not
required to enter their existing password. This could allow an attacker
to construct a URL that when activated during a valid web session, will
change the user's password to an arbitrary value. Since the attack can
only be effective using a user's existing session ID, this form of
attack is also known as Session Riding[2].

For example, to change the root user's password to "test", the following
URL would have to be visited by the root user while logged in to the
Management Interface:

https://address-of-the-vmware-server/sx-
users?op=setUsr&ag=&rg=&nm=root&hd=%2Froot&pw=test&pwc=test&grpSlct=

Causing the user to view the URL can be achieved through a number of
techniques, such as sending an email with the URL inserted as the source
of an image tag such as:

<img src="https://address-of-the-vmware-server/sx-
users?op=setUsr&ag=&rg=&nm=root&hd=%2Froot&pw=test&pwc=test&grpSlct=">

or including the image on a website that the user is coerced into
viewing, etc.

The likelihood of a successful attack is increased by the presence of a
Cross Site Scripting vulnerability [3] in the syslog viewer
functionality. By combining the two issues, it is possible for a
remote, unauthenticated attacker to change the root user's password
whenever that user views the syslog through the Management Interface.
For example, for an attacker to change the root user's password to
"test", an attacker could log in to the interface using the following
username:

</div><img src="/sx-
users?op=setUsr&ag=&rg=&nm=root&hd=%2Froot&pw=test&pwc=test&grpSlct=">

When the root user views the syslog through the Management Interface,
the link will be followed and the password changed.

-- Recommendations --

Upgrade to a version of the VMware ESX product that does not exhibit
this issue.

-- CVE --

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2005-3618 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardises names for
security problems.

-- References --

[1] http://www.vmware.com/products/esx/
[2] http://www.securenet.de/papers/Session_Riding.pdf
[3] c051114-003 (VMware ESX Server Password Disclosure in Log issue)

-- Revision --

a. Initial release.
b. Minor edits.
c. Released.

-- Distribution --

The information contained within this advisory is supplied "as-is" with
no warranties or guarantees of fitness of use or otherwise. Corsaire
accepts no responsibility for any damage caused by the use or misuse of
this information.

-- Disclaimer --

The information contained within this advisory is supplied "as-is" with
no warranties or guarantees of fitness of use or otherwise. Corsaire
accepts no responsibility for any damage caused by the use or misuse of
this information.

-- About Corsaire --

Corsaire are a leading information security consultancy, founded in 1997
in Guildford, Surrey, UK. Corsaire bring innovation, integrity and
analytical rigour to every job, which means fast and dramatic security
performance improvements. Our services centre on the delivery of
information security planning, assessment, implementation, management
and vulnerability research.

A free guide to selecting a security assessment supplier is available at
http://www.penetration-testing.com

Copyright 2005-2006 Corsaire Limited. All rights reserved.

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