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Security Response to CAN-2004-0230: Audit Warns of Possible Denial of Service Vulnerability (1535)


A security software audit warns that an ESX Server machine may have the security vulnerability described at:

How can I protect the server? Does VMware have a fix for this?


TCP implementations that use a large window size make it easier for remote attackers to guess sequence numbers that fall within the window. An attacker could potentially supply an acceptable sequence number, along with a forged source IP and TCP port, to inject a TCP RST or SYN packet into the data stream. Used successfully, this could result in a denial of service attack.

For clients accessing TCP services on an ESX Server machine — such as the VMware Management Interface — this could mean an inability to use the service, due to recurrent connection losses. Virtual machines would continue to run under these circumstances.

VMware has no plans to fix this at the present time, as it is not a serious security threat. If you notice frequent unexplained loss of connections to your ESX Server machine, VMware recommends you use intrusion detection software.

For links to other VMware security articles, refer to


1535; urlz; alertz; Nessus; 12213

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