CVE-1999-0813 in cfingerd
Summary
by MITRE
Cfingerd with ALLOW_EXECUTION enabled does not properly drop privileges when it executes a program on behalf of the user, allowing local users to gain root privileges.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0813 affects the cfingerd daemon, a service that provides finger protocol functionality for network information retrieval. This daemon operates on TCP port 79 and is commonly used in Unix-like systems to provide user information lookup services. The specific flaw exists when the cfingerd service is configured with the ALLOW_EXECUTION parameter enabled, which permits execution of arbitrary programs through the finger protocol interface. This configuration creates a critical security risk that directly violates fundamental privilege separation principles in system security architecture.
The technical implementation flaw stems from improper privilege handling within the cfingerd daemon's execution mechanism. When a user submits a command through the finger protocol while ALLOW_EXECUTION is enabled, the daemon fails to properly drop elevated privileges before executing the requested program. This privilege escalation occurs because the service maintains root privileges throughout the execution process, allowing maliciously crafted commands to be executed with the highest system permissions. The vulnerability represents a classic privilege escalation issue that aligns with CWE-276, which describes improper privilege management in software systems. The flaw essentially creates a backdoor execution path where local users can bypass normal access controls and execute commands with root privileges, fundamentally undermining the principle of least privilege that forms the foundation of secure system design.
The operational impact of this vulnerability is severe and far-reaching for any system running cfingerd with the vulnerable configuration. Local attackers who can access the finger service can exploit this weakness to execute arbitrary commands with root privileges, potentially leading to complete system compromise. This vulnerability enables attackers to install backdoors, modify critical system files, extract sensitive data, or disable security mechanisms. The attack vector is particularly dangerous because it requires minimal authentication - simply access to the finger service port is sufficient for exploitation. From an adversary perspective, this vulnerability maps directly to ATT&CK technique T1068, which covers privilege escalation through the exploitation of software vulnerabilities. The ease of exploitation combined with the high impact makes this a critical vulnerability that could be leveraged in automated attack scenarios targeting systems with improperly configured finger services.
Mitigation strategies for this vulnerability should focus on immediate configuration changes and system hardening measures. The most effective immediate solution is to disable the ALLOW_EXECUTION parameter in cfingerd configuration files, which eliminates the attack surface entirely. System administrators should also implement proper access controls and network segmentation to limit exposure of the finger service to trusted networks only. Additionally, regular security audits should verify that no unnecessary services are running with elevated privileges, and privilege separation mechanisms should be enforced through proper service configuration. The vulnerability highlights the importance of principle of least privilege implementation and proper privilege management in system services, which should be enforced through comprehensive security policies and regular vulnerability assessments. Organizations should also consider implementing intrusion detection systems to monitor for unusual finger protocol activity and ensure that all services running with elevated privileges are properly audited for similar privilege escalation vulnerabilities.