CVE-2021-34741

CVE-2021-34741 describes a denial-of-service (DoS) vulnerability in the email scanning algorithm of Cisco AsyncOS software for Cisco Email Security Appliance (ESA). This flaw, stemming from insufficient input validation, allows an unauthenticated, remote attacker to exhaust CPU resources by sending a crafted email. With a CVSS score of 7.5 (High), the vulnerability is easily exploitable over the network with low attack complexity, leading to a complete denial of service for email processing. There is no evidence of active exploitation, public exploit code, or significant community discussion, and it is not listed in CISA's KEV catalog.