CVE-2005-2146 in Tectia Server
Summary
by MITRE
SSH Tectia Server 4.3.1 and earlier, and SSH Secure Shell for Windows Servers, uses insecure permissions when generating the Secure Shell host identification key, which allows local users to access the key and spoof the server.
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Analysis
by VulDB Data Team • 07/24/2017
The vulnerability identified as CVE-2005-2146 represents a critical security flaw in SSH Tectia Server versions 4.3.1 and earlier, as well as in SSH Secure Shell for Windows Servers. This issue stems from the insecure handling of file permissions during the generation of Secure Shell host identification keys, creating a significant attack vector that compromises the integrity of SSH communications. The flaw specifically affects the cryptographic infrastructure that establishes trust between SSH clients and servers, undermining the fundamental security model that SSH protocols rely upon for secure remote access.
The technical implementation of this vulnerability involves the improper setting of file permissions when SSH host identification keys are generated during server installation or configuration. Typically, SSH host keys should be protected with restrictive permissions that prevent unauthorized access, particularly by non-privileged local users. However, the affected software implementations fail to properly secure these keys, often leaving them readable by any local user account. This insecure permission model directly violates security best practices and creates a scenario where malicious local users can extract the host key material, enabling them to impersonate the SSH server and potentially intercept or manipulate encrypted communications.
From an operational impact perspective, this vulnerability creates a severe threat to the authentication integrity of SSH services. When local users can access the host identification key, they gain the capability to perform server spoofing attacks, where they can present themselves as the legitimate SSH server to connecting clients. This allows for man-in-the-middle attacks where attackers can intercept sensitive information, modify communications, or establish unauthorized access to systems that rely on SSH for secure remote administration. The implications extend beyond simple privilege escalation, as this vulnerability can compromise the entire trust model that SSH implementations depend upon for secure network communications.
The vulnerability aligns with CWE-732, which specifically addresses inadequate permissions for critical security resources, and represents a classic example of how insufficient access control mechanisms can undermine cryptographic security. From an ATT&CK framework perspective, this vulnerability maps to T1566, which covers phishing techniques, and T1078, which addresses valid accounts, as attackers can leverage the compromised host key to establish unauthorized access. Organizations using affected SSH implementations face significant risk of credential theft, data interception, and unauthorized system access, particularly in environments where SSH is used for administrative access to critical infrastructure. The attack surface is particularly concerning in multi-user environments where local privilege escalation opportunities exist.
Mitigation strategies for this vulnerability require immediate implementation of proper file permission controls on SSH host key files, ensuring that these critical security resources are accessible only to the SSH service account and system administrators. System administrators should verify that host key files are protected with restrictive permissions that prevent unauthorized reading, typically requiring permissions such as 600 or 640, depending on the specific implementation. Additionally, organizations should implement regular security audits to verify that SSH configurations maintain appropriate access controls and consider implementing automated monitoring solutions that can detect unauthorized access attempts to cryptographic key material. The most effective long-term solution involves upgrading to patched versions of the affected SSH implementations that properly enforce secure key file permissions, as well as implementing comprehensive security policies that govern access to critical system resources.