CVE-2021-34781

CVE-2021-34781 is a denial-of-service vulnerability affecting Cisco Firepower Threat Defense (FTD) Software, Cisco Firepower Management Center Virtual Appliance, and Cisco Sourcefire Defense Center in multi-instance deployments. It stems from improper error handling during SSH connection establishment. An unauthenticated, remote attacker can exploit this by sending a high rate of crafted SSH connections, leading to resource exhaustion and a DoS condition requiring manual device reload. With a CVSS score of 7.5 (High), this vulnerability has a low attack complexity and no user interaction is required. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.