CVE-1999-0197 in finger
Summary
by MITRE
finger 0@host on some systems may print information on some user accounts.
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Analysis
by VulDB Data Team • 10/26/2025
The vulnerability described in CVE-1999-0197 represents a significant information disclosure issue within the finger protocol implementation on certain Unix-like systems. This flaw allows unauthorized users to retrieve potentially sensitive user account information by executing a simple command structure targeting the finger daemon. The vulnerability specifically manifests when a user or attacker runs the command finger 0@host where the '0' serves as a special identifier that can trigger the disclosure of user account details from the target system.
The technical root cause of this vulnerability lies in the improper handling of special user identifiers within the finger daemon's processing logic. When the finger service receives a request with a numeric identifier of zero, the daemon fails to properly validate or sanitize this input before proceeding with account enumeration. This lack of proper input validation creates an information disclosure channel that can reveal usernames, account status information, and potentially other account-related metadata to any user who can access the finger service. The vulnerability operates at the application layer and specifically targets the network service implementation rather than underlying system components.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data that can be leveraged for subsequent attacks. The disclosed user account information can serve as a foundation for password spraying attacks, social engineering attempts, or targeted exploitation of specific user accounts. The vulnerability affects systems where the finger service is enabled and accessible, potentially exposing all user accounts that have not been properly secured or restricted. This issue particularly impacts environments where the finger service remains active despite being deprecated due to security concerns, as the service continues to operate with minimal security controls.
This vulnerability aligns with CWE-200, which describes information disclosure vulnerabilities where sensitive information is exposed to unauthorized actors. The attack pattern follows typical reconnaissance techniques documented in the MITRE ATT&CK framework under the initial access and reconnaissance phases. The finger protocol itself has been deprecated for decades due to security concerns, making systems that still run finger services particularly vulnerable to such information disclosure attacks. Organizations should consider implementing network segmentation, disabling unnecessary services, and ensuring proper access controls to prevent exploitation of this and similar legacy service vulnerabilities.
Mitigation strategies for CVE-1999-0197 should focus on disabling the finger service entirely on affected systems, as the protocol is inherently insecure and has been superseded by more secure alternatives. Network administrators should conduct comprehensive audits to identify systems running finger services and ensure these services are either disabled or properly secured with access controls. The implementation of firewall rules to block finger service ports, typically port 79, provides an additional layer of protection. System hardening measures should include disabling the finger daemon service through service management tools and ensuring that no legacy services remain active on the network. Regular vulnerability scanning and system audits help identify and remediate instances of this and similar deprecated services that pose ongoing security risks to organizational infrastructure.