An issue was discovered in Heimdal PRO 2.2.190. As part of the scanning feature, a process called md.hs writes an executable called CS1.tmp to C:\windows\TEMP. Afterwards the executable is run.

It is possible for an attacker to create the file first, let md.hs overwrite it, and then rewrite the file in the window between md.hs closing the file and executing it. This can be exploited via opportunistic locks and a high priority thread. The vulnerability is triggered when a scan starts.

NOTE: any affected Heimdal products are completely unrelated to the Heimdal vendor of a Kerberos 5 product on the h5l.org web site.