Vulnerability Note VU#856689

VMware NAT Service vulnerable to buffer overflow via FTP PORT/EPRT commands

Original Release date: 21 Dec 2005 | Last revised: 23 Dec 2005


The VMware NAT Service used in multiple VMware products contains a buffer overflow in the way it handles FTP PORT and EPRT commands. An attacker could execute arbitrary code with the privileges of the NAT service or cause a denial of service.


VMware virtualization software provides Network Address Translation (NAT) for guest systems to access networks. The VMware NAT Service does not adequately validate parameters to the PORT and EPRT commands. As a result, specially crafted PORT or EPRT commands can trigger a buffer overflow. VMware Workstation, GSX Server, ACE, and Player products for Windows, Linux, and Solaris host platforms are affected. Additional information is available in VMware Knowledge Base Answer ID 2000.

To exploit this vulnerability, an attacker would need to convince a user to run code provided by the attacker on a VMware guest/virtual system. The attacker could then cross the boundary of the guest system and run arbitrary code within the context of the NAT process on the VMware host system. This attack vector may be of particular concern to users who intentionally run untrusted code in VMware environments. An attacker could also exploit this vulnerability remotely if the VMware NAT Service is configured to forward connections to guest/virtual systems. By default, the VMware NAT Service is not configured to forward connections, and in either scenario it may be necessary for the attacker to connect to an FTP server in order to issue crafted PORT or EPRT commands.


An attacker could execute arbitrary code with the privileges of the VMware NAT Service (Local System on Windows platforms, root on Linux platforms) or cause a denial of service.


This vulnerability is addressed in:

  • VMware Workstation 5.5.1
  • VMware GSX Server 3.2.1
  • VMware ACE 1.0.2
  • VMware Player 1.0.1
The latest releases of these products are available from the VMware Download Center.

Disable VMware NAT Service

Disable the VMware NAT Service as described in VMware Knowledge Base Answer ID 2002.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
VMwareAffected-21 Dec 2005
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



This vulnerability was reported by Tim Shelton.

This document was written by Art Manion.

Other Information

  • CVE IDs: CVE-2005-4459
  • Date Public: 21 Dec 2005
  • Date First Published: 21 Dec 2005
  • Date Last Updated: 23 Dec 2005
  • Severity Metric: 4.36
  • Document Revision: 24


If you have feedback, comments, or additional information about this vulnerability, please send us email.