Microsoft has received a report of an unexpected behavior in the way that the Windows Firewall User Interface handles malformed entries in the Windows Registry. By creating malformed Windows Firewall exception entries in the Windows Registry, an exception could be created in the firewall that would not be displayed in the Windows Firewall User Interface. However, this exception is displayed by the command line firewall administration tools.
It is important to note that this is not a vulnerability. Administrative privileges are required to access the associated section of the Windows Registry that contains this configuration information. By using documented methods to manage and create Windows Firewall exceptions, it is unlikely that a malformed registry entry will be produced which would exhibit this behavior. It is more likely that an attacker who has already compromised the system would create such malformed registry entries with intent to confuse a user.
Install this update to ensure that a firewall exception created via the registry is listed in the Windows Firewall interface the same as if the exception was created in the interface itself. After you install this update, you may have to restart your computer. This download is available running genuine Microsoft Windows.
Download: Update for Windows XP (KB897663)