What potential vulnerabilities lurk within widely used network technologies?
A critical flaw has emerged within Cisco Meraki’s VPN offerings, particularly impacting their AnyConnect VPN server on Meraki MX and Z Series Teleworker Gateway devices. Identified as an uninitialized variable error during the SSL VPN session establishment, this vulnerability permits remote attackers to enact denial-of-service (DoS) conditions on the VPN service.
This vulnerability particularly necessitates valid VPN user credentials, meaning only authenticated users can exploit the issue. When successfully executed, the flaw can cause the VPN server to crash, resulting in the immediate termination of all active VPN sessions. This not only requires users to reauthenticate but disrupts business continuity for any organization relying on Cisco Meraki for secure remote access. Cisco has classified this vulnerability under CWE-457 (Use of Uninitialized Variable), underscoring its critical nature.
The scope of this vulnerability is significantly severe, affecting numerous Cisco Meraki models, including but not limited to MX64, MX100, and Z4C, with a CVSS score of 8.6 indicating a critical risk level. Persistent exploitation of this flaw could render new SSL VPN connections impossible, crippling remote access entirely. Organizations are, as a result, faced with heightened operational risks, which encompass increased downtime, increased helpdesk costs, and potential threats to compliance and customer trust. Moreover, devices running affected firmware are particularly vulnerable, underlining the urgency for timely software updates.
To exploit the vulnerability, attackers can send specially crafted HTTPS requests to the VPN server. Once authenticated, they need only to send crafted data within SSL VPN session setup messages. Upon receiving such harmful requests, the server inevitably encounters a failure state and then restarts.
In response to the situation, Cisco has issued software updates to remedy the vulnerability. Organizations are strongly advised to apply these updates immediately, as no effective workarounds currently exist.
Additionally, monitoring for unusual VPN session requests is recommended to detect potential exploitation attempts before they cause significant service disruption or operational chaos. Failure to address the flaw carries risks that go beyond mere service interruptions, potentially undermining an organization’s overall security posture.
