OpenSSH-portable (OpenSSH) 3.6.1p1 and earlier with PAM support enabled immediately sends an error message when a user does not exist, which allows remote attackers to determine valid usernames via a timing attack.
lab.mediaservice.net/advisory/2003-01-openssh.txt
lists.grok.org.uk/pipermail/full-disclosure/2003-April/004815.html
marc.info/?l=bugtraq&m=105172058404810&w=2
marc.info/?l=bugtraq&m=106018677302607&w=2
www.redhat.com/support/errata/RHSA-2003-222.html
www.redhat.com/support/errata/RHSA-2003-224.html
www.securityfocus.com/bid/7467
www.turbolinux.com/security/TLSA-2003-31.txt
cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A445