Mandriva Linux Security Advisory 2010-054 – Pam_krb5 2.2.14 through 2.3.4 generates different password prompts depending on whether the user account exists, which allows remote attackers to enumerate valid usernames. This update provides the version 2.3.5 of pam_krb5, which is not vulnerable to this issue.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/86919/MDVSA-2010-054.txt
Source: https://packetstormsecurity.com/files/86919/Mandriva-Linux-Security-Advisory-2010-054.html