Microsoft on Monday issued a warning concerning a vulnerability in how Windows resolves hostnames, and is offering steps for systems administrators to work around the problem until a fix is issued.
The issue affects hostnames that do not include a fully qualified domain name (FQDN). A fully qualified domain name is a domain name that specifies the node’s position in the DNS tree hierarchy and is often used for sub sections of domains or for functions. A fully qualified domain is distinguishable by a period after the top-level extension, like “.com.”
This means third-level domains or deeper are vulnerable, such as mail.domainname.com or us.dbase.domainname.com. There are, however, mitigating factors, as detailed on the Microsoft Security Research Center alert page.
Microsoft has also issued several suggested workarounds until a patch is issued. These include creating a Proxy Auto-Configuration file, disabling Automatically Detect Settings in Internet Explorer, disabling DNS devolution and configuring a domain suffix search list.
Microsoft has not received any reports of customers being impacted by the vulnerability. It said it will decide what steps to take upon completion of its investigation. This could include issuing an out-of-cycle security update or simply waiting until Patch Tuesday, depending on customer needs. The next Patch Tuesday will be December 11.