Microsoft has released software updates that correct this vulnerability.
Microsoft Internet Explorer contains a vulnerability that could allow an unauthenticated, remote attacker to disclose sensitive information.
The vulnerability is due to an unspecified error in Internet Explorer when the browser is not configured to run in Protected Mode. An unauthenticated, remote attacker could obtain access to the contents of a file on a targeted user's system if the full path is known. The attacker would first need to create a malicious website and convince a targeted user to view the website.
Proof-of-concept code is publicly available.
Microsoft has confirmed this vulnerability and released updated software.
The following products are vulnerable when not running in Protected Mode:
Internet Explorer version 5.01 SP4 and prior Internet Explorer version 6.0 SP1 and prior Internet Explorer version 7.0 Internet Explorer version 8.0
To exploit the vulnerability, an attacker must persuade a targeted user to visit a malicious website. This action will typically require the use of social engineering tactics, such as sending a link to the website by means of an e-mail message, instant messaging, or other form of communication.
Users of Windows Vista, Windows Server 2008, and Windows 7 are protected in the default configuration because Internet Explorer runs in Protected Mode by default on these systems.
Microsoft has released a security bulletin at the following link: MS10-035
An unauthenticated, remote attacker could exploit the vulnerability to access sensitive information.
The vulnerability is in the Internet Explorer HTML rendering engine, which uses URLMON when loading a local file. The engine tries to check the MIME type of a file for a positive match. However, if the file does not have a known type and is treated as HTML due to a redirection, the file type will default to text/html.
An unauthenticated, remote attacker could exploit this vulnerability by creating a crafted web page with script that uses a dynamic OBJECT tag and is designed to load a local file that does not have an assigned MIME type as text/html. An exploit could disclose the contents of the file to the attacker. To exploit the vulnerability, the attacker must know the name and the full path of the file.
Administrators are advised to apply the appropriate updates.
Users are advised to run Internet Explorer in Protected Mode whenever possible.
Users are advised not to open e-mail messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in e-mail messages are safe, they are advised not to open them.
Users should verify that unsolicited links are safe to follow.
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
Version 2, February 4, 2010, 11:50 AM: Additional technical information is available to describe the Microsoft Internet Explorer remote information disclosure vulnerability. Proof-of-concept code is also available.
Version 1, February 3, 2010, 7:00 PM: Microsoft Internet Explorer contains a vulnerability that could allow an unauthenticated, remote attacker to disclose sensitive information. Updates are not available.
Home Edition Base, SP1, SP2, SP3 | Professional Edition Base, SP1, SP2, SP3 | Professional x64 (AMD/EM64T) Base, SP1, SP2
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