CVE-2001-0156 in VShell
Summary
by MITRE
VShell SSH gateway 1.0.1 and earlier has a default port forwarding rule of 0.0.0.0/0.0.0.0, which could allow local users conduct arbitrary port forwarding to other systems.
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Analysis
by VulDB Data Team • 05/18/2019
The vulnerability identified in CVE-2001-0156 affects VShell SSH gateway version 1.0.1 and earlier implementations, presenting a significant security flaw in network access control mechanisms. This issue stems from a misconfiguration in the port forwarding rules that govern how the SSH gateway handles network connections. The default configuration establishes a rule set that permits unrestricted port forwarding operations, creating an attack vector that can be exploited by local users to bypass normal network security controls. The vulnerability is particularly concerning because it operates at the network gateway level where traffic is typically monitored and controlled, making it a critical point of failure in network security infrastructure.
The technical flaw manifests through the improper implementation of access control lists within the SSH gateway's configuration. The default port forwarding rule of 0.0.0.0/0.0.0.0 represents a wildcard configuration that allows any source IP address to establish port forwarding connections to any destination IP address. This configuration violates fundamental security principles of least privilege and network segmentation, as it provides unrestricted access to network services that should normally be restricted based on user roles, network zones, or security policies. The vulnerability is classified under CWE-284, which deals with improper access control, specifically in the context of network access controls and port forwarding mechanisms. From an operational perspective, this flaw enables attackers to potentially establish connections to internal network services that would normally be protected by firewalls or other network security controls.
The operational impact of this vulnerability extends beyond simple unauthorized network access, as it can facilitate more sophisticated attack patterns that align with techniques described in the MITRE ATT&CK framework under the T1021 category for remote services and T1071 for application layer protocol usage. Local users who exploit this vulnerability can potentially map local ports to remote systems, enabling them to access internal services that should be restricted to authorized users only. This capability can lead to data exfiltration, lateral movement within networks, and the establishment of persistent access points. The vulnerability is particularly dangerous in enterprise environments where SSH gateways serve as critical access points for remote administration and network connectivity, as it essentially removes the network security boundary that the gateway was designed to enforce.
Mitigation strategies for this vulnerability require immediate configuration changes to restrict the default port forwarding rules to specific IP ranges and authorized users only. Organizations should implement strict access control lists that limit port forwarding capabilities to only those users and systems that require such access for legitimate administrative purposes. The recommended approach involves configuring explicit allow lists for port forwarding rules rather than relying on default wildcard configurations. Additionally, regular security audits should be conducted to ensure that SSH gateway configurations maintain appropriate security boundaries and that no unauthorized changes have been made to access control policies. Network monitoring should be enhanced to detect unusual port forwarding activities that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of secure configuration management and the necessity of implementing principle of least privilege controls in network security infrastructure, particularly for critical access points like SSH gateways that handle sensitive administrative functions.