Marcomp Blog

Microsoft Warns Of Zero-Day Flaw In Older Versions Of IE
Pointer reference flaw could enable attackers to run their own code on IE machines, software giant says

Nov 24, 2009 | 01:44 PM
By Tim Wilson
DarkReading

Microsoft says it is investigating public reports of a vulnerability in older versions of Internet Explorer that could enable attackers to inject their own code onto Windows PCs.

In a security advisory, Microsoft says the vulnerability primarily affects Internet Explorer 6 and 7, as well as related service packs. The older IE 5.01 Service Pack 4 and the newer IE 8 are not affected.

“The vulnerability exists as an invalid pointer reference of Internet Explorer,” Microsoft says. “It is possible under certain conditions for a CSS/Style object to be accessed after the object is deleted. In a specially-crafted attack, Internet Explorer attempting to access a freed object can lead to running attacker-supplied code.”

Although the vulnerability is public and no patch is yet available, Microsoft says it does not know of any active exploits yet. Once it finishes its investigation, Microsoft says it will respond, possibly through an out-of-cycle update or a scheduled Patch Tuesday release.

Microsoft also says it is working with partners to “monitor the threat landscape and take action against malicious sites that attempt to exploit this vulnerability.”

As a workaround, Microsoft says users of the affected versions of IE could run their browsers in restricted mode (Enhanced Security Configuration). Microsoft also says systems configured with fewer user rights may be less likely to be affected.

New attack fells Internet Explorer

The zero-day flaw is unreliable, but Symantec expects reliable exploits in the ‘near future’
By Robert McMillan , IDG News Service , 11/22/2009

A hacker has posted attack code that could be used to break into a PC running older versions of Microsoft’s Internet Explorer browser.

The code was posted Friday to the Bugtraq mailing list by an unidentified hacker. According to security vendor Symantec, the code does not always work properly, but it could be used to install unauthorized software on a victim’s computer.

Symantec has conducted further tests and confirmed that it affects Internet Explorer versions 6 and 7,” the company wrote on its Web site Saturday. “We expect that a fully-functional reliable exploit will be available in the near future.”

Security consultancy Vupen Security has also confirmed that the attack works, saying it worked on a Windows XP Service Pack 3 system running IE 6 or IE7. Neither company was able to confirm that the attack worked on Microsoft’s latest browser, IE 8.

Symantec did not report that the attack is being used by cyber-criminals, but because Internet Explorer is so popular, this type of code is highly coveted by hackers. If the software does pop up in online attacks, it will put pressure on Microsoft to rush out an emergency patch, ahead of its regularly scheduled Dec. 8 security update. Microsoft could not be reached Saturday for a comment on the issue.

Together, IE 6 and IE 7 command close to 40 percent of the browser market.

The flaw lies in the way Internet Explorer retrieves certain Cascading Style Sheet (CSS) objects, used to create a standardized layout on Web pages. For the attack to work, the hacker would have to lure a victim to a Web page that contained maliciously encoded JavaScript, Symantec said. This technique has emerged as a favorite way for hackers to install their malicious software on computers in recent years.

“To minimize the chances of being affected by this issue, Internet Explorer users should ensure their antivirus definitions are up to date, disable JavaScript and only visit Web sites they trust until fixes are available from Microsoft,” Symantec said.

The IDG News Service is a Network World affiliate.