Critical Vulnerability in FrontPage Server Extensions

Microsoft publicized a critical new vulnerability for Web servers running its FrontPage Server Extensions.

FrontPage Server Extensions (FPSE) are a set of Web server-side tools to accommodate Web sites built and administered using Microsoft's FrontPage Web site building tool. FPSE support Web forms and other FrontPage-based dynamic content. FPSE are installed by default in IIS versions 4.0, 5.0 and 5.1. Microsoft has recommended previously that users disable the FrontPage Server Extensions on servers where they are not needed.

The vulnerability is exploited through a specially crafted request for a particular type of Web file. The vulnerability works differently on FrontPage Server Extensions 2000 and FrontPage Server Extensions 2002. In the 2000 version, exploiting the flaw creates a denial of service condition on the Web server. In the 2002 version, the flaw results in a buffer overflow that could result in privilege elevation.

The specific component of FPSE involved in the vulnerability is called the SmartHTML Interpreter. Microsoft noted in its security bulletin about the vulnerability that the IIS Lockdown tool disables the SmartHTML Interpreter. Another mitigating factor is that servers aren't vulnerable to the attack if the FPSE have been disabled.

The fix will be included in Windows 2000 Service Pack 4 and Windows XP Service Pack 2. The bulletin and patch are available at:

About the Author

Scott Bekker is editor in chief of Redmond Channel Partner magazine.

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