Cisco Email Security Appliance (ESA) and Web Security Appliance (WSA) are vulnerable to a man-in-the-middle attack, caused by improper certificate validation when establishes TLS connections. An attacker could exploit this vulnerability to launch a man-in-the-middle attack and gain access to the communication channel between endpoints to spoof a trusted host and then extract sensitive information or alter certain API requests.
Cisco Email Security Appliance (ESA)
Cisco Web Security Appliance (WSA)
Upgrade to the Cisco Small Business 220 Series Smart Switches firmware releases 220.127.116.11 and later from https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-wsa-cert-vali-n8L97RW