IIS 4.0 and 5.0 allows remote attackers to read documents outside of the web root, and possibly execute arbitrary commands, via malformed URLs that contain UNICODE encoded characters, aka the "Web Server Folder Traversal" vulnerability.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A44
https://exchange.xforce.ibmcloud.com/vulnerabilities/5377
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-078