The gss_userok function in appl/ftp/ftpd/gss_userok.c in Heimdal 0.7.2 does not allocate memory for the ticketfile pointer before calling free, which allows remote attackers to have an unknown impact via an invalid username. NOTE: the vulnerability was originally reported for ftpd.c, but this is incorrect.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2007-5939)