VMware has released several patches that address vulnerabilities in older ESX and ESXi versions. These patches should be installed as soon as possible to preserve the security of VMware installations.
<blockquote>VMware ROM Overwrite Privilege Escalation

A flaw in the way port-based I/O is handled allows for modifying
Read-Only Memory that belongs to the Virtual DOS Machine.
Exploitation of this issue may lead to privilege escalation on
Guest Operating Systems that run Windows 2000, Windows XP
32-bit, Windows Server 2003 32-bit or Windows Server 2003 R2
32-bit.

VMware would like to thank Derek Soeder of Ridgeway Internet
Security, L.L.C. for reporting this issue to us.

The Common Vulnerabilities and Exposures project (<a href="http://cve.mitre.org/" target="_blank">cve.mitre.org</a>)
has assigned the name CVE-2012-1515 to this issue.</blockquote>
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