CVE-2024-20498 in Meraki MX
Summary
by MITRE • 10/02/2024
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.
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Analysis
by VulDB Data Team • 07/03/2025
The vulnerability identified as CVE-2024-20498 represents a critical security flaw in Cisco Meraki MX and Z Series Teleworker Gateway devices that specifically affects the AnyConnect VPN server implementation. This vulnerability stems from inadequate input validation mechanisms within the SSL VPN session establishment process, creating a pathway for remote attackers to disrupt service availability. The affected devices operate as network infrastructure components that provide secure remote access capabilities to organizations, making this vulnerability particularly concerning for enterprise security operations. The vulnerability exists in the server-side processing of client parameters during SSL VPN session negotiation, where proper sanitization and validation of incoming data is insufficient to prevent malicious input from causing system instability.
The technical exploitation of this vulnerability occurs through the submission of crafted HTTPS requests to the VPN server component of affected devices. The insufficient parameter validation allows attackers to inject malformed or specially constructed data that triggers unexpected behavior within the AnyConnect service. When these crafted requests are processed, they cause the VPN server to experience a restart condition that results in immediate disruption of existing SSL VPN connections. This restart operation is not a graceful shutdown but rather an abrupt service interruption that forces all active connections to terminate. The vulnerability affects the core operational functionality of the VPN service, creating a denial of service condition that impacts legitimate users who require network access. The attack vector is particularly dangerous because it requires no authentication credentials, making it accessible to any remote attacker who can reach the device's network interface.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise business continuity and user productivity. When the AnyConnect VPN server restarts, all active remote connections are terminated, forcing users to reauthenticate and reestablish their VPN sessions. This process creates significant user experience degradation and can be particularly disruptive in mission-critical environments where continuous network access is required. The vulnerability's potential for sustained attacks means that attackers could maintain prolonged disruption of VPN services, preventing new connections from being established entirely. This condition effectively blocks legitimate users from accessing organizational resources through the VPN service, creating a complete denial of service scenario for remote workers and administrators who depend on these connections for their daily operations.
Organizations should implement immediate mitigations to address this vulnerability, including network segmentation to limit access to affected devices and monitoring for anomalous traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic example of how insufficient parameter validation can lead to service disruption. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers "Endpoint Denial of Service," and demonstrates how attackers can leverage service-specific weaknesses to achieve availability compromise. Cisco has released patches and firmware updates to address this issue, and organizations should prioritize applying these updates to their affected devices. Additionally, network administrators should consider implementing rate limiting and connection monitoring to detect and prevent exploitation attempts, as the vulnerability's exploitation does not require authentication and can be automated at scale.