vchkpw program in vpopmail before version 4.8 does not properly cleanse an untrusted format string used in a call to syslog, which allows r…

vchkpw program in vpopmail before version 4.8 does not properly cleanse an untrusted format string used in a call to syslog, which allows remote attackers to cause a denial of service via a USER or PASS command that contains arbitrary formatting directives.