Microsoft has acknowledged that a "zero-day" vulnerability exists in Internet Explorer 8 (IE8), confirming reports made by multiple security firms.
Microsoft on Friday said it was investigating public reports of a vulnerability in Internet Explorer 8, adding that it was aware of attacks that attempt to exploit the vulnerability.
Internet Explorer 6, Internet Explorer 7, Internet Explorer 9, and Internet Explorer 10 are not affected by the vulnerability.
This is a remote code execution vulnerability, which exists in the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated. The vulnerability may corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user within Internet Explorer. An attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website.
Security engineers at Invincea and have verified that IE8 on Windows 7 is vulnerable.
By default, Internet Explorer on Windows Server 2003, Windows Server 2008, and Windows Server 2008 R2 runs in a restricted mode that is known as Enhanced Security Configuration. Microsoft says that this mode mitigates this vulnerability.
In addition, supported versions of Microsoft Outlook, Microsoft Outlook Express, and Windows Mail open HTML email messages in the Restricted sites zone. The Restricted sites zone, which disables script and ActiveX controls, helps reduce the risk of an attacker being able to use this vulnerability to execute malicious code. If a user clicks a link in an email message, the user could still be vulnerable to exploitation of this vulnerability through the web-based attack scenario.
On completion of this investigation, Microsoft may provide a solution through its monthly security update release process (scheduled for Tuesday, May 14.) , or an out-of-cycle security update.