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

Summaryinfo

A vulnerability, which was classified as critical, has been found in Cisco Meraki MX and Meraki Z. This affects an unknown part of the component AnyConnect VPN Server. Performing a manipulation results in out-of-bounds write. This vulnerability is known as CVE-2024-20501. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Cisco Meraki MX and Meraki Z (affected version unknown). It has been classified as critical. This affects an unknown functionality of the component AnyConnect VPN Server. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. CWE is classifying the issue as CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. This is going to have an impact on availability. The summary by CVE is:

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 at sec.cloudapps.cisco.com. This vulnerability is uniquely identified as CVE-2024-20501 since 11/08/2023. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (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). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Cisco

Name

• Meraki MX
• Meraki Z

License

• commercial

Website

• Vendor: https://www.cisco.com/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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