Title: Unchecked Buffer in ISAPI Extension Could Enable Compromise of IIS 5.0 Server Date: 01 May 2001 Software: Windows 2000 Server Windows 2000 Advanced Server Windows 2000 Datacenter Server Impact: Run code of attacker's choice, in Local System context Bulletin: MS01-023
Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-023.asp.
Windows 2000 introduced native support for the Internet Printing Protocol (IPP), an industry-standard protocol for submitting and controlling print jobs over HTTP. The protocol is implemented in Windows 2000 via an ISAPI extension that is installed by default on all Windows 2000 servers but which can only be accessed via IIS 5.0.
A security vulnerability results because the ISAPI extension contains an unchecked buffer in a section of code that handles input parameters. This could enable a remote attacker to conduct a buffer overrun attack and cause code of her choice to run on the server. Such code would run in the Local System security context. This would give the attacker complete control of the server, and would enable her to take virtually any action she chose.
The attacker could exploit the vulnerability against any server with which she could conduct a web session. No other services would need to be available, and only port 80 (HTTP) or 443 (HTTPS) would need to be open. Clearly, this is a very serious vulnerability, and Microsoft strongly recommends that all IIS 5.0 administrators install the patch immediately. Alternatively, customers who cannot install the patch can protect their systems by removing the mapping for Internet Printing ISAPI extension.