A denial of service flaw was found in the way Pacemaker, an advanced, scalable high-availability cluster resource manager for Linux-HA (Heartbeat) and/or Corosync, performed authentication and processing of remote connections in certain circumstances. In general Pacemaker used a blocking socket (without a timeout) to wait for authentication credentials to arrive. When Pacemaker was configured to allow remote Cluster Information Base (CIB) cluster's configuration / cluster's resources management, a remote attacker could use this flaw to cause Pacemaker to block indefinitely (preventing it from serving another requests).

Important Note: In the default configuration of Pacemaker in Red Hat Enterprise Linux 6 the remote CIB management feature / functionality is turned off.