By Richard Speed
Publication Date: 2026-05-28 16:30:00
OSes
May security update trips over hostnames of a very specific length
Windows Server 2016 might be long in the tooth but that isn’t about to stop Microsoft breaking stuff.
The May 12 security update introduced another bug for administrators to worry about. According to Microsoft, if the server hostname is exactly 15 characters long (like, for example, THEY-NEVER-TEST), domain controller discovery might fail.
In the notes for the glitch, Microsoft wrote: “When the hostname is 15 characters long, DCLocator calls (for example, using nltest /dsgetdc: /pdc) will return ERROR_INVALID_PARAMETER, preventing applications and administrative tools from locating a domain controller.”
In other words, anything that depends on a domain controller lookup might stop working. As an example, Microsoft gave Distributed File System (DFS) Namespace management, which would certainly be inconvenient. DFS Namespaces is a Windows Server role…