Cisco Meraki MX and Z3 Teleworker Gateway VPN Denial of Service Vulnerability

A vulnerability in the Cisco AnyConnect VPN server of Cisco Meraki MX and Cisco Meraki Z3 Teleworker Gateway devices could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

This vulnerability is due to insufficient validation of client-supplied parameters while establishing an SSL VPN session. An attacker could exploit this vulnerability by crafting a malicious request and sending it to the affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to crash and restart, resulting in the failure of the established SSL VPN connections and forcing remote users to initiate a new VPN connection and re-authenticate. A sustained attack could prevent new SSL VPN connections from being established.

Note: When the attack traffic stops, the Cisco AnyConnect VPN server recovers gracefully without requiring manual intervention.

Cisco Meraki has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-meraki-mx-vpn-dos-vnESbgBf [“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-meraki-mx-vpn-dos-vnESbgBf”]