CVE-2000-1195 in Openlinux Edesktop
Summary
by MITRE
telnet daemon (telnetd) from the Linux netkit package before netkit-telnet-0.16 allows remote attackers to bypass authentication when telnetd is running with the -L command line option.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 04/08/2019
The vulnerability described in CVE-2000-1195 represents a critical authentication bypass flaw in the telnet daemon implementation within the Linux netkit package. This issue specifically affects versions of netkit-telnet prior to 0.16 where the telnetd service operates with the -L command line option. The telnet protocol has historically been a fundamental networking service for remote terminal access, but its implementation has consistently faced security challenges due to inherent design weaknesses and poor security practices in early implementations. The vulnerability exploits a fundamental flaw in how authentication is handled when the daemon is configured to log user activities through the -L option, creating a pathway for unauthorized access that directly violates the principle of least privilege and secure authentication mechanisms.
The technical flaw manifests when telnetd is executed with the -L flag, which enables logging of user sessions to a specified file. Under normal circumstances, this logging feature should not interfere with the authentication process, but in vulnerable versions the daemon fails to properly validate authentication credentials before establishing the logging mechanism. This creates a race condition or logic flaw where an attacker can establish a connection and bypass the authentication checks entirely. The vulnerability is particularly insidious because it leverages legitimate system functionality to create an unauthorized access vector, making it difficult to detect through standard security monitoring. The flaw essentially allows an attacker to establish a telnet session without proper credentials, effectively providing a backdoor into systems that rely on telnet for remote access.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it represents a fundamental breakdown in the security model of network services. Systems running vulnerable versions of telnetd become susceptible to remote exploitation without requiring any prior knowledge of valid user credentials or passwords. This vulnerability directly affects the confidentiality, integrity, and availability of affected systems, as unauthorized users can gain access to sensitive data, execute commands with potentially elevated privileges, and compromise the overall security posture of network infrastructure. The attack vector is particularly dangerous in environments where telnet is used for administrative access, as it can lead to complete system compromise and unauthorized modification of critical system files. This vulnerability also demonstrates the importance of proper input validation and authentication flow control in network services, as the flaw exists in the basic service logic rather than in a specific cryptographic implementation.
Mitigation strategies for CVE-2000-1195 focus primarily on immediate patching and configuration changes to prevent exploitation. The most effective solution involves upgrading to netkit-telnet version 0.16 or later, which includes proper authentication validation even when the -L logging option is enabled. Organizations should also consider disabling the -L command line option if logging is not essential for operations, as this removes the vulnerable code path entirely. Security administrators should implement network segmentation to limit access to telnet services and consider replacing telnet with more secure alternatives such as SSH, which provides encrypted communication and robust authentication mechanisms. Additionally, monitoring for unauthorized telnet connections and implementing intrusion detection systems can help identify exploitation attempts. This vulnerability aligns with CWE-287, which addresses improper authentication, and maps to ATT&CK technique T1021.004 for remote services, highlighting the need for proper service configuration and authentication controls in network infrastructure security practices.