CVE-2002-0424 in Efingerd
Summary
by MITRE
efingerd 1.61 and earlier, when configured without the -u option, executes .efingerd files as the efingerd user (typically "nobody"), which allows local users to gain privileges as the efingerd user by modifying their own .efingerd file and running finger.
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Analysis
by VulDB Data Team • 06/07/2018
The vulnerability identified as CVE-2002-0424 affects efingerd versions 1.61 and earlier, representing a critical privilege escalation flaw in the finger daemon implementation. This vulnerability stems from improper file execution handling within the efingerd service configuration, specifically when the daemon operates without the -u option parameter. The core issue lies in the daemon's failure to properly validate or sanitize user-provided .efingerd files, creating an exploitable condition that allows local users to manipulate their own configuration files and subsequently execute arbitrary code with elevated privileges.
The technical flaw manifests through a path traversal and code execution vulnerability where users can modify their personal .efingerd files to contain malicious shell commands or scripts. When the efingerd service processes these files without proper user context validation, it executes the contents as the efingerd user account, which typically runs with minimal privileges but still possesses system access capabilities. This behavior directly violates the principle of least privilege and creates a direct path for privilege escalation attacks. The vulnerability is classified under CWE-22 as Improper Limitation of a Pathname to a Restricted Directory, and CWE-78 as Improper Neutralization of Special Elements used in an OS Command, both of which are fundamental security weaknesses that enable unauthorized code execution.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with a persistent foothold within the system that operates at the efingerd user level. This creates opportunities for further exploitation including lateral movement, data exfiltration, and potential elevation to root privileges depending on the system configuration. Attackers can leverage this vulnerability to maintain access to compromised systems while avoiding detection through normal privilege escalation methods. The attack vector is particularly concerning because it requires minimal user interaction beyond standard finger protocol usage, making it difficult to distinguish from legitimate system behavior.
Mitigation strategies for CVE-2002-0424 should prioritize immediate patching of efingerd installations to versions that properly handle user file execution or implement proper input validation. System administrators should ensure that efingerd is configured with appropriate security options including the -u flag to enforce proper user context handling. Additionally, implementing file system permissions controls and monitoring for unauthorized modifications to .efingerd files can help detect exploitation attempts. The vulnerability aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and T1548.001 which addresses 'Abuse Elevation Control Mechanism' through local privilege escalation techniques. Organizations should also consider disabling the finger protocol entirely if not required for operational necessity, as this eliminates the attack surface entirely while maintaining system security posture.