A NULL pointer dereference vulnerability was found in the Libreswan package. When an IKEv1 ISAKMP SA Informational Exchange packet contains a Delete/Notify payload followed by further Notifies that act on the ISAKMP SA, such as a duplicated Delete/Notify message, a NULL pointer dereference on the deleted state occurs. This flaw allows a malicious client or attacker to send a malformed IKEv1 Delete/Notify packet, causing a crash and restarting the libreswan pluto daemon. When sent continuously, this could lead to a denial of service attack.