Cisco Meraki MX and Z Series AnyConnect VPN Denial of Service Vulnerability (CVE-2025-20212)

CVE number = CVE-2025-20212

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

To exploit this vulnerability, the attacker must have valid VPN user credentials on the affected device.

This vulnerability exists because a variable is not initialized when an SSL VPN session is established. An attacker could exploit this vulnerability by supplying crafted attributes while establishing an SSL VPN session with an affected device.

A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to restart, resulting in the failure of the established SSL VPN sessions and forcing remote users to initiate a new VPN connection and reauthenticate. A sustained attack could prevent new SSL VPN connections from being established.

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

This vulnerability affects the following Cisco Meraki products if they are running a vulnerable release of Cisco Meraki MX firmware and have Cisco AnyConnect VPN enabled:

MX64
MX64W
MX65
MX65W
MX67
MX67C
MX67W
MX68
MX68CW
MX68W
MX75
MX84
MX85
MX95
MX100
MX105
MX250
MX400
MX450
MX600
vMX
Z3
Z3C
Z4
Z4C

Note: Cisco AnyConnect VPN is supported on Cisco Meraki MX and Cisco Meraki Z Series devices that run Cisco Meraki MX firmware releases 16.2 and later, except for Cisco Meraki MX64 and MX65, which support Cisco AnyConnect VPN only if they are running Cisco Meraki MX firmware releases 17.6 and later.

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