The Microsoft MS01-014 and MS01-016 patches for IIS 5.0 and earlier introduce a memory leak which allows attackers to cause a denial of service via a series of requests.
An administrative script from IIS 3.0, later included in IIS 4.0 and 5.0, allows remote attackers to cause a denial of service by accessing the script without a particular argument, aka the "Absent Directory Browser Argument" vulnerability.
IIS 4.0 allows remote attackers to obtain the internal IP address of the server via an HTTP 1.0 request for a web page which is protected by basic authentication and has no realm defined.
Frontpage Server Extensions allows remote attackers to determine the name of the anonymous account via an RPC POST request to shtml.dll in the /_vti_bin/ virtual directory.
IIS 3.0 and 4.0 on x86 and Alpha allows remote attackers to cause a denial of service (hang) via a malformed GET request, aka the IIS "GET" vulnerability.
FTP service in IIS 4.0 and earlier allows remote attackers to cause a denial of service (resource exhaustion) via many passive (PASV) connections at the same time.