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.