Microsoft released the second installment of its now monthly security bulletins, patching three software holes in Windows systems that it said were "critical" security risks and a fourth problem with Microsoft Office that the company rated "important."

Taken together, the security holes could allow attackers to set up Web pages to take advantage of vulnerable systems and read files or run attack code on a remote user's Windows machine, Microsoft said.

One bulletin, MS03-049, affects Windows 2000 and Windows XP workstations and fixes a critical buffer overrun vulnerability in a Windows service called the Workstation Service, which manages requests for files or printing services on a LAN. That service is turned "on" by default in Windows and could be compromised by an attacker using an improperly formatted network message that was sent to a vulnerable machine.

A second bulletin, MS03-051, patches two critical problems that were discovered in Microsoft's FrontPage Server Extensions, which are installed by default with the Internet Information Services (IIS) on certain versions of Windows 2000 and allows technical staff to create, manage and add features to Web pages.

Microsoft said that it fixed a buffer overrun in the FrontPage Server Extensions that could enable an attacker to place and run attack code on a vulnerable machine, as well as a flaw in the way that a component called SmartHTML interpreter works that made it vulnerable to denial-of-service attacks.

The Redmond, Wash., company also issued a new cumulative security patch, MS03-048, for the Internet Explorer (IE) Web browser. The new patch updates previous cumulative patches for IE and sews up five new vulnerabilities in the product, including a problem with the browser's cross domain security model, which governs how different Web sites share information and interact with the Windows operating system.

The fourth patch, MS03-050, fixes a security hole in some versions of Microsoft's Excel spreadsheet and Word word processing products that could enable an attacker to embed an attack in a small program known as a macro. Machines running vulnerable versions of those products could have malicious code placed and run on their Windows system after opening an infected spreadsheet or Word document, Microsoft said.

The IDG News Service is a Network World affiliate.