New IE vulnerability affects all versions of Windows

Chrome, Firefox browsers appear to be safe from the threat

Microsoft released Security Advisory 2501696 in response to a scripting vulnerability in Internet Explorer that affects all versions of Windows.

The security hazard is found in the MIME Encapsulation of Aggregate HTML (MHTML) protocol handler. The attach mechanism is similar to a server-side cross-site-scripting (XSS) exploit, in which a malicious script could run on a user's computer after clicking on a link.

While this vulnerability could be exploited by hackers, the chances of an attack are slim, according to some software security analysts.

"At first glance today's advisory looks grim because it affects every supported Windows platform," wrote Andrew Storms, director of information and technology at software security firm nCircle, in a released statement.  "However, even though the proof of concept code is public, carrying out an attack using this complicated cross site scripting-like bug will not be easy."

While there currently is no patch to fix the vulnerability, Microsoft suggested a workaround. This mitigation approach disables MHTML handler scripting by setting all corresponding keys in the Windows registry. Microsoft issued a "Fix it" in a KnowledgeBase article to automate the workaround.

Wolfgang Kandek, CTO of Qualys, offered another option to avoid the vulnerability: use an alternative browser.

"While the vulnerability is located in a Windows component, Internet Explorer is the only known attacker vector," Kandek wrote in a blog posting.  "Firefox and Chrome are not affected in their default configuration, as they do not support MHTML without the installation of specific add-on modules."

The hole was first brought to the attention by individuals on the WooYun Web site. This is the same site that divulged information about the vulnerability in the CSS handler of Internet Explorer in December.

Coupled with a handful of security concerns earlier this month, Microsoft has been busy with multiple vulnerabilities as of late. "2011 is not off to an auspicious start for Microsoft's security staff," wrote Storms. "In early January Jonathan Ness posted an explanation of five public security bugs Microsoft was tracking to the SRD blog. Today, just two short weeks later, we have another one to add to the list."

About the Author

Chris Paoli is the associate Web editor for 1105 Enterprise Computing Group's Web sites, including,, and

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Reader Comments

Wed, Feb 2, 2011

why does the government continue to waste valuable taxpayer resources on microsoft products. there are so many free alternatives that are much safer in terms of security. there is even an opensource free version of solaris, opensolaris, freeBSD, etc in addition to all the linux distros. openoffice is as good or better than ms office and it is also free. it's a shame the government has given a defacto monopoly on one large company for at least 15 years now. it's time they opened up the playing field to competition.

Tue, Feb 1, 2011

Looks like Windows 98 isn't effected. If it wasn't for the implementation of the sicking flash application, 98 would be running just fine.

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