Patch Tuesday: Both Microsoft and Mozilla Issue Fixes

— -- Microsoft today released three software updates that patch critical security flaws in its products, including a patch for an Internet Explorer vulnerability that was first reported last week. The company also released patches for Microsoft Word and for a feature of the Windows operating system that is used by a number of applications.

All three of the patches, which Microsoft calls "updates," are rated "critical," meaning that the flaws they fix could allow malicious code to be installed on a user's computer with very little user action. The updates affect current versions of Windows and Internet Explorer as well as certain older versions of Word, according to Stephen Toulouse, security program manager with Microsoft's security response center.

The Internet Explorer and Windows patches appear to be the most significant, as the flaws they address could both be used by an attacker to take control of a user's system via a maliciously encoded Web page, said Neel Mehta, team leader of X-Force research with security vendor Internet Security Systems. The IE bug is significant because security experts have already shown a way that it could be exploited by an attacker, he said.

And the Mozilla Foundation on Tuesday fixed a number of security bugs in its Firefox Web browser, many of which will also be patched in upcoming releases of Mozilla's Thunderbird e-mail client and Mozilla Internet software suite.

None of the bugs had been publicly divulged before Tuesday, and they are generally not considered to be critical, according to Chris Hofmann, director of engineering with the Mozilla Foundation.

"There are a collection of ten reports that have come in over the past couple of months from security researchers," he said. "Most of these involve quite a bit of user interaction to participate in the potential exploit."

Still, the Foundation advises that all users upgrade to the new software, which also includes "stability" improvements, according to the Mozilla.org Web site.

The bugs are patched in version 1.0.5 of the Firefox browser. A Thunderbird update, also numbered 1.0.5, is expected Wednesday, Hofmann said. The patches will also be applied in version 1.7.9 of the Mozilla suite, which will be released sometime within the week, he said.

The Firefox update can be found here.

Last week, Microsoft issued a workaroundto Internet Explorer's problem, which concerns a file used by IE called Javaprxy.dll. However, Tuesday's patch fixes the underlying problem, ISS's Mehta said.

ISS is also concerned about the Windows vulnerability, which relates to a feature called the Microsoft Color Management Module. This software is used to ensure that colors look the same when they are being rendered on different types of hardware, and is employed by a number of widely used applications, including Microsoft Outlook and IE, Mehta said.

"Our initial analysis shows it being pretty conducive to exploitation," Mehta said. "Any application that uses the built-in Windows facilities to show JPEG images, or possibly some other images, could be an attack vector for this vulnerability."

In fact, Microsoft has already privately been made aware of exploits of this flaw, Toulouse said.

The Word vulnerability, which could allow an attacker to gain control of a user's system when a maliciously encoded Word document is opened, does not affect the most recent version of the word processor. However, users of Word 2000 and 2002 will need to install the patch, Toulouse said.

The three patches are detailed in Microsoft Security Bulletins MS05-35, MS05-36, and MS05-37, which can be found here. A new version of a previously released bulletin, MS05-33, was also released Tuesday after Microsoft discovered that the Windows bug that it addresses also affects the company's Services for Unix 2.0 and 2.1. products, Toulouse said.

All three of the patches will probably require a reboot in order to take effect, Toulouse said. "If the files are in use when the update is applied, and in these cases they're pretty much going to be, that is what forces a reboot," he said.