Researchers: Newest Microsoft IE patch flawed

IDG News Service - A new patch designed to address six serious security vulnerabilities in Microsoft Corp.'s Internet Explorer doesn't fix all the problems it purports to, according to security researchers.
The patch, which was released Wednesday, is designed to fix a cross-site scripting problem and other security and privacy flaws affecting Internet Explorer Versions 5.01 through 6.0 and the Outlook e-mail client (see story). However, the patch fixes the cross-site scripting issue on only one of the listed browsers and fails to address a second vulnerability altogether, according to two security researchers who sent e-mail to the Bugtraq security e-mail list after the patch's release.
According to Microsoft's explanation of the issues, the first flaw can be exploited only when a user clicks on an HTML link on a Web page or in an e-mail message. But that's not true, according to both Thor Larholm, a security researcher who has discovered a number of Microsoft vulnerabilities and maintains a list of unpatched Internet Explorer holes online, and the Israeli security group GreyMagic Software, which has also discovered a number of browser vulnerabilities. They said code embedded in an HTML file can automatically execute. As a result, users can unwittingly launch malicious code simply by opening an infected e-mail message.
The patch doesn't completely fix the problem because the flaw resides in the dialogArguments component of Internet Explorer, which isn't addressed by the patch, both researchers said. Furthermore, though Microsoft said the flaw exists only in Internet Explorer 6, both researchers maintain that the problem is also found in Internet Explorer 5.01 and 5.5.
"Microsoft is aware of the issues and is investigating the reports," a Microsoft spokesman said. Microsoft maintains that the patch does what the company said, but the company is also investigating the researchers' claims, the spokesman said.

After further testing of the patch, both Larholm and GreyMagic said that the patch also fails to adequately address a second vulnerability that it claims to fix, a problem that could allow an attacker to remotely read documents on a PC.

In the original vulnerability, Cascading Style Sheets (CSS), a component of HTML, could be used to remotely read files on an affected PC, according to GreyMagic's original advisory. Though the patch claims to address this issue, GreyMagic posted code on its Web site today demonstrating that the vulnerability can still be exploited by using a URL that redirects the user, as opposed to accessing the files directly. Larholm sent an e-mail about the issue and his testing of it, as well as GreyMagic's update, to Bugtraq today.

Microsoft was not immediately available for comment on the new reports.

Related stories:

• Netscape, Mozilla hole allows remote text viewing, May 1, 2002


• IE flaw exploited for MSN Messenger worm, Feb.14, 2002

Reprinted with permission from

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