The (1) elog.c and (2) elogd.c components in elog before 2.5.7 r1558-4 generate different responses depending on whether or not a username is valid, which allows remote attackers to determine valid usernames.
bugs.debian.org/cgi-bin/bugreport.cgi/0003-r1472-Do-not-distinguish-between-invalid-user-name-and-invalid-password.txt?bug=349528%3Bmsg=15%3Batt=3
bugs.debian.org/cgi-bin/bugreport.cgi?bug=349528
secunia.com/advisories/18783
www.debian.org/security/2006/dsa-967
www.securityfocus.com/bid/16579
exchange.xforce.ibmcloud.com/vulnerabilities/24706