CVE-2024-20509 in Meraki MX
Summary
by MITRE • 10/02/2024
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 hijack an AnyConnect VPN session or cause a denial of service (DoS) condition for individual users of the AnyConnect VPN service on an affected device.
This vulnerability is due to weak entropy for handlers that are used during the VPN authentication process as well as a race condition that exists in the same process. An attacker could exploit this vulnerability by correctly guessing an authentication handler and then sending crafted HTTPS requests to an affected device. A successful exploit could allow the attacker to take over the AnyConnect VPN session from a target user or prevent the target user from establishing an AnyConnect VPN session with the affected device.
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Analysis
by VulDB Data Team • 07/03/2025
The vulnerability identified as CVE-2024-20509 represents a critical security flaw in Cisco Meraki MX and Z Series Teleworker Gateway devices that operate Cisco AnyConnect VPN services. This weakness stems from insufficient cryptographic entropy during the authentication handler generation process, creating predictable session identifiers that can be exploited by unauthorized parties. The vulnerability specifically targets the authentication mechanisms that establish and maintain VPN sessions, making it particularly dangerous for organizations relying on these devices for secure remote access. The affected devices operate as network infrastructure components that handle sensitive corporate communications, making this flaw a significant concern for enterprise security posture.
The technical implementation of this vulnerability involves two primary components that compound the security risk. First, the weak entropy in handler generation creates predictable authentication tokens that can be guessed through brute force or statistical analysis methods. This weakness maps directly to CWE-330, which addresses insufficient entropy in random number generators and cryptographic operations. Second, a race condition exists within the same authentication process, allowing attackers to exploit timing vulnerabilities during session establishment. The race condition aspect aligns with CWE-362, which covers concurrent execution using shared resources without proper synchronization, enabling attackers to manipulate session states. These combined weaknesses create a scenario where an unauthenticated remote attacker can successfully intercept or disrupt VPN sessions without requiring valid credentials.
The operational impact of CVE-2024-20509 extends beyond simple session hijacking to include potential service disruption and data compromise. When exploited, attackers can seamlessly take over active VPN sessions, potentially gaining access to corporate networks, sensitive applications, and confidential data without detection. The denial of service component prevents legitimate users from establishing new VPN connections, effectively blocking remote access for authorized personnel. This vulnerability directly impacts the CIA triad by compromising confidentiality through session interception, integrity through potential data manipulation, and availability through service disruption. Organizations using these devices for remote workforce management face significant risk of unauthorized network access, especially in environments where these devices serve as primary gateways for teleworker connectivity.
Mitigation strategies for CVE-2024-20509 should focus on both immediate defensive measures and long-term architectural improvements. Cisco has released patches addressing the entropy and race condition issues, which organizations must deploy immediately to remediate the vulnerability. Network administrators should implement additional monitoring for unusual authentication patterns and session establishment attempts that could indicate exploitation attempts. The ATT&CK framework suggests implementing network segmentation to limit lateral movement if exploitation occurs, while also establishing robust logging and alerting mechanisms around VPN authentication events. Organizations should also consider implementing multi-factor authentication for VPN access, although this does not directly address the specific vulnerability. Regular security assessments of network infrastructure components and maintaining updated vulnerability management processes are essential for preventing similar issues. The vulnerability highlights the importance of proper cryptographic implementation and race condition handling in network security devices, emphasizing that even minor implementation flaws can create significant security risks for entire organizations.