Red Hat Security Advisory 2015-1154-01 – Libreswan is an implementation of IPsec & IKE for Linux. IPsec is the Internet Protocol Security and uses strong cryptography to provide both authentication and encryption services. These services allow you to build secure tunnels through untrusted networks such as virtual private network. A flaw was discovered in the way Libreswan’s IKE daemon processed certain IKEv1 payloads. A remote attacker could send specially crafted IKEv1 payloads that, when processed, would lead to a denial of service.