(RHSA-2015:1640) Moderate: pam security update

Pluggable Authentication Modules (PAM) provide a system whereby
administrators can set up authentication policies without having to
recompile programs to handle authentication.

It was discovered that the _unix_run_helper_binary() function of PAM’s
unix_pam module could write to a blocking pipe, possibly causing the
function to become unresponsive. An attacker able to supply large passwords
to the unix_pam module could use this flaw to enumerate valid user
accounts, or cause a denial of service on the system. (CVE-2015-3238)

Red Hat would like to thank Sebastien Macke of Trustwave SpiderLabs for
reporting this issue.

All pam users are advised to upgrade to this updated package, which
contains a backported patch to correct this issue.