Recent attack on Google in China related with IE vulnerability.

Microsoft is investigating a report of a publicly exploited vulnerability in Internet Explorer. This advisory contains information about which versions of Internet Explorer are vulnerable as well as workarounds and mitigations for this issue.

Our investigation so far has shown that Internet Explorer 5.01 Service Pack 4 on Microsoft Windows 2000 Service Pack 4 is not affected, and that Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4, and Internet Explorer 6, Internet Explorer 7 and Internet Explorer 8 on supported editions of Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2 are affected.

The vulnerability exists as an invalid pointer reference within Internet Explorer. It is possible under certain conditions for the invalid pointer to be accessed after an object is deleted. In a specially-crafted attack, in attempting to access a freed object, Internet Explorer can be caused to allow remote code execution.

At this time, we are aware of limited, active attacks attempting to use this vulnerability against Internet Explorer 6. We have not seen attacks against other affected versions of Internet Explorer. We will continue to monitor the threat environment and update this advisory if this situation changes. On completion of this investigation, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs.

We are actively working with partners in our Microsoft Active Protections Program (MAPP) and our Microsoft Security Response Alliance (MSRA) programs to provide information that they can use to provide broader protections to customers. In addition, we’re actively working with partners to monitor the threat landscape and take action against malicious sites that attempt to exploit this vulnerability.

Microsoft continues to encourage customers to follow the “Protect Your Computer” guidance of enabling a firewall, applying all software updates and installing anti-virus and anti-spyware software. Additional information can be found at Security at home.

Mitigating Factors:

Protected Mode in Internet Explorer on Windows Vista and later Windows operating systems limits the impact of the vulnerability.
In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attacker’s Web site.
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less affected than users who operate with administrative user rights.
By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone.
By default, all supported versions of Microsoft Outlook, Microsoft Outlook Express, and Windows Mail open HTML e-mail messages in the Restricted sites zone. The Restricted sites zone helps mitigate attacks that could try to exploit this vulnerability by preventing Active Scripting and ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, the user could still be vulnerable to exploitation of this vulnerability through the Web-based attack scenario.

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