Cisco Meraki MX/Meraki Z AnyConnect VPN Server out-of-bounds write

Summaryinfo

A vulnerability classified as critical was found in Cisco Meraki MX and Meraki Z. Affected by this issue is some unknown functionality of the component AnyConnect VPN Server. Such manipulation leads to out-of-bounds write. This vulnerability is traded as CVE-2024-20499. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Cisco Meraki MX and Meraki Z (version unknown) and classified as critical. Affected by this issue is an unknown function of the component AnyConnect VPN Server. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is availability. CVE summarizes:

Multiple vulnerabilities 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. These vulnerabilities are due to insufficient validation of client-supplied parameters while establishing an SSL VPN session. An attacker could exploit these vulnerabilities by sending a crafted HTTPS request to the VPN server of 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 connections 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 gracefully without requiring manual intervention.

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability is handled as CVE-2024-20499 since 11/08/2023. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 07/03/2025).

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 vulnerability database at Tenable (241198). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• Cisco

Name

• Meraki MX
• Meraki Z

License

• commercial

Website

• Vendor: https://www.cisco.com/

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion