Microsoft issues seven security patches, two critical

Microsoft Corp. on Tuesday released seven security patches covering a wide array of the company's products. Two of those patches fix holes that Microsoft deemed "critical" and warned could allow remote attackers to take control of vulnerable Windows systems.

The software updates include fixes for previously unknown holes in Windows, including critical holes in the Windows Task Manager and HTML (Hypertext Markup Language) help features. The company also published a patch for a recent, publicly disclosed hole in the Windows Shell application programming interface (Shell API) and fixed a hole in older versions of the Internet Information Services (IIS) Web server that one expert said is well-suited for use in an Internet worm.

The seven updates, named MS04-018 through MS04-024, were released in accordance with the company's monthly patching schedule. At the top of the list were two patches, MS04-022 and MS04-023, that Microsoft said were "critical" and could allow remote attackers to run malicious code on affected Windows systems, according to the Microsoft Web page. (See: http://www.microsoft.com/technet/security/current.aspx.)

MS04-022 fixes a hole in Windows Task Scheduler, a Windows component that lets users schedule commands, programs or computer scripts to run at a specific time. A buffer overrun vulnerability in the Task Scheduler could allow a malicious hacker to place and run attack code on the vulnerable system, Microsoft said.

In buffer overrun attacks, malicious hackers purposely fill a buffer, or temporary data store, causing data, including malicious code written by the attacker, to spill over into other parts of the system's memory. Buffer overrun attacks can be used to shut down vulnerable systems, corrupt data, alter the way applications run or give attackers control over the systems.

Attackers could embed attacks on the Task Scheduler in a file on a Web page, then trick Windows users into visiting that page. Alternatively, a Task Scheduler file, called a JOB file, could be tailored to trigger the buffer overrun, Microsoft said.

MS04-023 fixes two more newly discovered critical holes in the Windows HTML help feature. One hole, in a component called showHelp, fixes an error in the way that Windows processes a type of help file known as a CHM file. If left unfixed, the flaw could allow a remote attacker to use specially crafted URLs (uniform resource locators) to run attack code on the vulnerable Windows system. Attackers would have to trick users into clicking on a malicious link, using a specially designed Web page, or a link embedded in an HTML format e-mail message, Microsoft said.

A second flaw in the way Windows checks data in help files also was patched by MS04-023. That vulnerability could allow an anonymous user to set up a Web site containing code designed to trigger the vulnerability. Attackers could also embed attack code in an HTML format e-mail message, Microsoft said.

In addition to those two critical fixes, Microsoft patched four holes rated "important," which indicates that exploitation could result in the compromising of data, but not the creation of an Internet worm. One of those patches is related to a widespread Web attack in late June in which hackers modified the configuration of Microsoft IIS Web servers, allowing malicious code to be appended to every HTML document served by the Web server