Cisco Meraki MX/Meraki Z AnyConnect VPN Server resource consumption

Summaryinfo

A vulnerability labeled as problematic has been found in Cisco Meraki MX and Meraki Z. This affects an unknown function of the component AnyConnect VPN Server. Executing a manipulation can lead to resource consumption. This vulnerability is registered as CVE-2024-20500. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic was found in Cisco Meraki MX and Meraki Z (the affected version unknown). This vulnerability affects an unknown part of the component AnyConnect VPN Server. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. CVE summarizes:

A vulnerability in the Cisco AnyConnect VPN server of Cisco Meraki MX and Cisco Meraki Z Series Teleworker Gateway devices could allow an unauthenticated, remote attacker to cause a DoS condition in the AnyConnect service on an affected device. This vulnerability is due to insufficient resource management when establishing TLS/SSL sessions. An attacker could exploit this vulnerability by sending a series of crafted TLS/SSL messages to the VPN server of an affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to stop accepting new connections, preventing new SSL VPN connections from being established. Existing SSL VPN sessions are not impacted. Note: When the attack traffic stops, the Cisco AnyConnect VPN server recovers gracefully without requiring manual intervention.

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability was named CVE-2024-20500 since 11/08/2023. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 241198 (Cisco Meraki 16.2 / 17 / 18.1 < 18.1.07.12 / 18.2 < 18.2.11.2 Multiple Vulnerabilities (cisco-sa-meraki-mx-vpn-dos-QTRHzG2)), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (241198) and EUVD (EUVD-2024-18215). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• Cisco

Name

• Meraki MX
• Meraki Z

License

• commercial

Website

• Vendor: https://www.cisco.com/

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Once again VulDB remains the best source for vulnerability data.

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