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Credit:
The information has been provided by Stephen de Vries.
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Vulnerable Systems:
* 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
Immune Systems:
* VMware ESX prior to 2.5.3 upgrade patch 3
* VMware ESX prior to 2.1.3 upgrade patch 2
* VMware ESX prior to 2.0.2 upgrade patch 2
VMware ESX Server is described 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 customized 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.
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 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 Information:
CVE-2005-3618
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