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Title: Flaw in Windows Media Player Skins Downloading could allow Code Execution (817787) Date: 07 May 2003 Software: Microsoft Windows Media Player 7.1 Microsoft Windows Media Player for Windows XP (Version 8.0) Impact: Arbitrary code execution Max Risk: Critical Bulletin: MS03-017
Microsoft encourages customers to review the Security Bulletins at: http://www.microsoft.com/technet/security/bulletin/MS03-017.asp http://www.microsoft.com/security/security_bulletins/ms03-017.asp
Microsoft Windows Media Player provides functionality to change the overall appearance of the player itself through the use of "skins". Skins are custom overlays that consist of collections of one or more files of computer art, organized by an XML file. The XML file tells Windows Media Player how to use these files to display a skin as the user interface. In this manner, the user can choose from a variety of standard skins, each one providing an additional visual experience. Windows Media Player comes with several skins to choose from, but it is relatively easy to create and distribute custom skins.
A flaw exists in the way Windows Media Player 7.1 and Windows Media Player for Windows XP handle the download of skin files. The flaw means that an attacker could force a file masquerading as a skin file into a known location on a user's machine. This could allow an attacker to place a malicious executable on the system.
In order to exploit this flaw, an attacker would have to host a malicious web site that contained a web page designed to exploit this particular vulnerability and then persuade a user to visit that site - an attacker would have no way to force a user to the site. An attacker could also embed the link in an HTML e-mail and send it to the user.
In the case of an e-mail borne attack, if the user was using Outlook Express 6.0 or Outlook 2002 in their default configurations, or Outlook 98 or 2000 in conjunction with the Outlook Email Security Update, then an attack could not be automated and the user would still need to click on a URL sent in the e-mail. However if the user was not using Outlook Express 6.0 or Outlook 2002 in their default configurations, or Outlook 98 or 2000 in conjunction with the Outlook Email Security Update, the attacker could cause an attack that could both place, then launch the malicious executable without the user having to click on a URL contained in an e-mail.
The attacker's code would run with the same privileges as the user: any restrictions on the user's ability to change the system would apply to the attacker's code.
Windows Media Player 9 Series is not affected by this issue.
By default, Outlook Express 6.0 and Outlook 2002 open HTML mails in the Restricted Sites Zone. In addition, Outlook 98 and 2000 open HTML mails in the Restricted Sites Zone if the Outlook Email Security Update, has been installed. Customers who use any of these products would be at no risk from an e-mail borne attack that attempted to automatically exploit these vulnerabilities.
The attacker would have no way to force users to visit a malicious web site. Instead, the attacker would need to lure them there, typically by getting them to click on a link that would take them to the attacker's site.
for information on obtaining this patch.
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