The Symantec Encryption Management Server (SEMS) product, prior to version 3.4.2 MP1, may be susceptible to a denial of service (DoS) exploit. A DoS attack is a type of attack whereby the perpetrator attempts to make a particular machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a specific host within a network.
https://support.symantec.com/en_US/article.SYMSA1458.html