A critical vulnerability fixed in mid-2018 has been resurrected in denial-of-service and information disclosure attempts against Cisco’s appliances Adaptive Security (ASA) and Firepower. The company is issuing a warning to its customers urging them to follow recommendations for proper mitigation actions. The vulnerability can be leveraged by an unauthenticated, remote attacker to cause the appliance to reload by sending it a crafted HTTP request. An attacker can also exploit this bug to view sensitive system information without authentication.
Source: https://www.bleepingcomputer.com/news/security/cisco-security-appliances-targeted-for-dos-attacks-via-old-bug/