CVE-2021-31604 in openvpn-monitor
Summary
by MITRE • 09/27/2021
furlongm openvpn-monitor through 1.1.3 allows CSRF to disconnect an arbitrary client.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2021-31604 affects the furlongm openvpn-monitor application version 1.1.3 and earlier, representing a significant security flaw that enables unauthorized users to perform cross-site request forgery attacks against the monitored openvpn service. This vulnerability specifically allows attackers to disconnect arbitrary clients from the openvpn server by exploiting the application's lack of proper anti-CSRF protections in its client management functions. The flaw resides in the application's web interface where administrative actions such as client disconnection are performed without adequate validation of the request source or authenticity of the user initiating the action.
The technical implementation of this vulnerability stems from the absence of anti-CSRF tokens or similar protection mechanisms within the openvpn-monitor's web forms and API endpoints that handle client disconnection requests. When an administrator or authorized user accesses the monitoring interface to disconnect a client, the application fails to verify that the request originates from a legitimate source within the same session or that the request was intentionally initiated by an authenticated user. This allows an attacker to craft malicious web pages or exploit existing vulnerabilities in other parts of the application to trick authenticated users into executing unintended disconnection commands against arbitrary clients.
The operational impact of this vulnerability extends beyond simple client disconnection, as it represents a critical compromise of the application's integrity and the underlying openvpn service's security posture. An attacker who successfully exploits this vulnerability can disrupt network connectivity for legitimate users, potentially causing service interruptions, unauthorized access to network resources, or even denial of service conditions within the VPN infrastructure. The vulnerability affects the availability and confidentiality of the VPN service, as unauthorized disconnections can be performed without the knowledge or consent of legitimate administrators or users. This flaw directly violates the principle of least privilege and can be leveraged to escalate attacks within environments where openvpn is used for secure remote access.
Organizations utilizing this vulnerable version of openvpn-monitor face significant risks including unauthorized network access, service disruption, and potential data exposure through compromised VPN connections. The vulnerability can be exploited through various attack vectors including phishing campaigns, compromised web pages, or by leveraging other vulnerabilities that allow code execution in the victim's browser context. From a cybersecurity perspective, this vulnerability aligns with CWE-352, which describes Cross-Site Request Forgery (CSRF) weaknesses in web applications, and can be mapped to ATT&CK technique T1566.001 for initial access through spearphishing attachments, or T1071.004 for application layer protocol usage in exploitation. The lack of proper input validation and session management in the application's client disconnection functionality creates a persistent security gap that can be exploited repeatedly by attackers without requiring additional privileges or complex attack chains.
The recommended mitigations for this vulnerability include immediate upgrading to a patched version of the openvpn-monitor application where anti-CSRF protections have been implemented. Organizations should also consider implementing additional security controls such as network segmentation, access controls, and monitoring for unauthorized client disconnection attempts. The application should be configured to require multi-factor authentication for administrative functions, and session management should be strengthened with proper token generation and validation mechanisms. Regular security assessments and vulnerability scanning should be performed to identify similar weaknesses in other web applications within the organization's infrastructure. Additionally, network administrators should implement logging and alerting for client disconnection events to detect and respond to unauthorized activities promptly.