Microsoft has issued a cumulative patch for Windows Media Player designed to patch three vulnerabilities, the most serious of which might permit an attacker to run arbitrary code on a victim's PC.

An advisory by Microsoft says that the most serious of the three problems is an information disclosure vulnerability, which it rates as severe.

The vulnerability results because of a flaw in how Windows Media Player handles certain types of licenses for secure media files when the media file is stored in the IE cache. Specifically, when a type of secure Windows Media file is opened, the media player erroneously returns information to the server that discloses the location of the IE cache.

If the attacker were able to cause an executable program to be stored in the cache, the location information obtained by this vulnerability could then be used to access content in the cache directly and bypass IE's cache security mechanisms. Attacks could be made using either maliciously constructed Web pages or HTML mails.

The patch also addresses a less severe privilege elevation bug which might enable an attacker who can physically log on locally to a Windows 2000 machine and run a program to obtain the same rights as the operating system.

Then there's a still less severe script execution vulnerability, which Microsoft says would be very difficult to exploit in practice because it involves tricking a victim into playing a specially formed media file and then viewing a maliciously constructed Web page.

With the patch, Microsoft has introduced a configuration change relating to file extensions associated with Windows Media Player. It is also debuting an optional security configuration feature for users who want to disable scripting functionality in Windows Media Player versions 7.x or higher. ®

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