IIS 4.0 and 5.0 does not properly perform ISAPI extension processing if a virtual directory is mapped to a UNC share, which allows remote attackers to read the source code of ASP and other files, aka the "Virtualized UNC Share" vulnerability.
Microsoft Site Server and Commercial Internet System (MCIS) do not set an expiration for a cookie, which could then be cached by a proxy and inadvertently used by a different user.