CVE-2005-2797 in OpenSSH
Summary
by MITRE
OpenSSH 4.0, and other versions before 4.2, does not properly handle dynamic port forwarding ("-D" option) when a listen address is not provided, which may cause OpenSSH to enable the GatewayPorts functionality.
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Analysis
by VulDB Data Team • 07/04/2019
The vulnerability described in CVE-2005-2797 affects OpenSSH versions prior to 4.2, specifically addressing a flaw in how the software handles dynamic port forwarding operations. This issue arises when the "-D" option is used without explicitly specifying a listen address, creating a potential security risk that could allow unauthorized access to network services. The flaw represents a critical misconfiguration in the software's network binding behavior that could be exploited by malicious actors to gain unintended network access.
The technical root cause of this vulnerability lies in the improper handling of network socket binding operations within OpenSSH's dynamic port forwarding implementation. When the "-D" flag is employed without a specified listen address, the system defaults to binding to all available network interfaces rather than restricting connections to localhost only. This behavior effectively enables GatewayPorts functionality automatically, which was not the intended operational mode for dynamic port forwarding. The flaw demonstrates a lack of proper input validation and network security boundary enforcement within the SSH daemon's configuration parsing logic.
The operational impact of this vulnerability is significant as it creates an unintended attack surface that could allow remote adversaries to establish connections to services running on the target system. An attacker could potentially leverage this flaw to bypass local network restrictions and access internal services that should only be reachable through the SSH tunnel. This vulnerability specifically affects the security model of SSH by weakening the isolation between the local network environment and external network access, creating potential for lateral movement and privilege escalation within compromised networks.
Organizations using OpenSSH versions prior to 4.2 should immediately implement mitigations including upgrading to version 4.2 or later where this vulnerability has been addressed. The recommended approach involves ensuring that all dynamic port forwarding operations explicitly specify listen addresses to prevent automatic binding to all interfaces. Additionally, system administrators should review their SSH configurations to disable unnecessary port forwarding capabilities and implement proper network segmentation controls. This vulnerability aligns with CWE-284, which addresses improper access control, and maps to ATT&CK technique T1021.004 for remote service attacks, highlighting the need for proper network boundary enforcement and access control mechanisms.
The flaw demonstrates a classic example of insufficient input validation and improper privilege management in network security software. Security practitioners should consider implementing network monitoring to detect unusual port binding patterns and establish proper firewall rules to restrict access to SSH services. Regular security assessments of network infrastructure should include verification of SSH configuration parameters and validation of default security settings. The vulnerability underscores the importance of maintaining current security software versions and implementing comprehensive network security policies to prevent unauthorized service exposure.