A newly discovered vulnerability CVE-2025-20212 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.

Background

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

A successful exploit can 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.

Code Snippet

Below is a sample code snippet that demonstrates how the CVE-2025-20212 vulnerability can be exploited:

import requests

# Replace 'TARGET_IP' with the target device's IP address
target_url = "https://TARGET_IP/";
crafted_data = {
    "invalid_variable": "sample_value"
}

# Replace 'USERNAME' and 'PASSWORD' with valid VPN user credentials
auth = requests.auth.HTTPBasicAuth('USERNAME', 'PASSWORD')

response = requests.post(target_url, data=crafted_data, auth=auth)

Original References

For more information on the CVE-2025-20212 vulnerability and additional details on how you can mitigate its effects on your network, we recommend referring to the original references provided by Cisco:

- Cisco Meraki Advisory on CVE-2025-20212 Vulnerability
- Cisco Security Advisory on CVE-2025-20212 Vulnerability

Exploit Details

An attacker who successfully exploits this vulnerability can cause the Cisco AnyConnect VPN server to restart, leading to a denial of service situation that affects all users connected via the SSL VPN sessions. Users connected to the VPN must reauthenticate to reconnect, and a sustained attack could potentially prevent any new connections from being established. This may adversely impact an organization's communication infrastructure and remote worker connectivity.

It is highly recommended to patch the affected devices and update the Cisco AnyConnect VPN server software to the latest version. For further assistance, reach out to Cisco Technical Assistance Center (TAC) or your local Cisco Meraki support for guidance.

Conclusion

The CVE-2025-20212 vulnerability poses a significant risk to organizations using the vulnerable Cisco AnyConnect VPN server software. It is essential to take immediate action by patching the affected devices and staying up-to-date on the latest security advisories. By taking these steps, organizations can help ensure the security and continued functionality of their remote access infrastructure.

Timeline

Published on: 04/02/2025 17:15:44 UTC