CVE-2021-41583 in vpn-user-portal
Summary
by MITRE • 09/24/2021
vpn-user-portal (aka eduVPN or Let's Connect!) before 2.3.14, as packaged for Debian 10, Debian 11, and Fedora, allows remote authenticated users to obtain OS filesystem access, because of the interaction of QR codes with an exec that uses the -r option. This can be leveraged to obtain additional VPN access.
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability CVE-2021-41583 affects the vpn-user-portal component known as eduVPN or Let's Connect! which is commonly deployed in enterprise and educational environments for secure remote access. This authentication portal serves as a gateway for users to establish VPN connections to organizational networks, making it a critical component in the overall security infrastructure. The issue manifests in versions prior to 2.3.14 and specifically impacts deployments packaged for Debian 10, Debian 11, and Fedora operating systems, indicating a widespread exposure across multiple Linux distributions. The vulnerability stems from improper handling of QR code generation and execution commands, creating a dangerous interaction that can be exploited by authenticated attackers to escalate their privileges and gain unauthorized access to the underlying operating system filesystem.
The technical flaw resides in the interaction between QR code generation and an exec command that utilizes the -r option, which is typically used for recursive operations in Unix-like systems. When users generate QR codes for VPN configuration, the system processes these codes through an execution mechanism that fails to properly sanitize or validate the input parameters. This creates a command injection vulnerability where maliciously crafted QR codes can be processed by the system and interpreted as executable commands. The -r option in this context becomes a critical vector for privilege escalation, as it allows recursive file system traversal and manipulation that can bypass normal access controls. According to CWE classification, this vulnerability maps to CWE-78, which describes improper neutralization of special elements used in OS commands, and CWE-22, which addresses improper limitation of a pathname to a restricted directory.
The operational impact of this vulnerability is severe and multi-layered, as it allows remote authenticated users to obtain direct operating system filesystem access without requiring additional credentials or privileges. An attacker who has already established a valid user session within the VPN portal can leverage this vulnerability to execute arbitrary commands on the host system with the privileges of the executing process. This can lead to complete system compromise, allowing attackers to access sensitive data, modify system configurations, or establish persistent backdoors. The vulnerability can be particularly dangerous in environments where the VPN portal serves as a gateway to internal networks, as it enables attackers to move laterally within the organization and potentially access critical infrastructure components. The ability to obtain additional VPN access through this vulnerability means that attackers can extend their reach beyond the initial compromise, creating a significant risk for organizations relying on this authentication mechanism.
Organizations should immediately upgrade to vpn-user-portal version 2.3.14 or later to address this vulnerability, as this represents the most direct and effective mitigation strategy. System administrators should also implement additional monitoring and logging of QR code generation activities and execution commands to detect anomalous patterns that might indicate exploitation attempts. Network segmentation and privilege separation should be reviewed to limit the potential impact if exploitation occurs, ensuring that the compromised portal component cannot directly access critical system resources. According to ATT&CK framework, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1078.004 (Valid Accounts: Cloud Accounts) as attackers can leverage the compromised portal to escalate privileges and potentially gain access to additional accounts or resources. Security teams should also consider implementing web application firewalls and input validation mechanisms to prevent malicious QR code content from being processed through the vulnerable execution paths. Regular security assessments of authentication portals and VPN components should be conducted to identify and remediate similar vulnerabilities that could provide similar attack vectors.