CVE-1999-0198 in finger
Summary
by MITRE
finger .@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-1999-0198 relates to the finger daemon service running on Unix-based systems, which traditionally provides user information lookup services across networks. This particular flaw manifests when the finger command is executed with the syntax ".@host" on certain systems, potentially exposing user account information that should remain private or restricted. The finger protocol operates on TCP port 79 and was widely used in early network environments for user identification and system information retrieval. The vulnerability represents a significant information disclosure issue as it allows unauthorized users to gather sensitive account data from remote systems without proper authentication or authorization.
The technical nature of this vulnerability stems from improper input validation and access control mechanisms within the finger daemon implementation. When the command ".@host" is processed, the service fails to properly sanitize the input or enforce appropriate access restrictions, leading to information leakage about user accounts on the target system. This behavior typically occurs due to inadequate boundary checking and insufficient validation of the host parameter in the finger request. The flaw exists at the application layer and demonstrates poor security practices in protocol implementation, where the service does not adequately distinguish between legitimate and malicious requests. This type of vulnerability falls under CWE-20, which describes improper input validation, and represents a classic case of insufficient access control that allows unauthorized information disclosure.
The operational impact of CVE-1999-0198 extends beyond simple information disclosure, as the leaked user account information can serve as a foundation for further attacks within the network environment. Attackers can use the gathered account data to identify active users, potentially map network topology, or conduct targeted social engineering campaigns. The vulnerability enables reconnaissance activities that can precede more sophisticated attacks such as credential brute-forcing or privilege escalation attempts. Network administrators face the challenge of maintaining system integrity when such information leakage occurs, as it provides attackers with valuable intelligence about system users and potential entry points. This vulnerability particularly affects systems where finger services are enabled and accessible over the network, making it a concern for legacy systems or environments where network services have not been properly secured.
Mitigation strategies for this vulnerability involve multiple layers of defensive measures that address both immediate exposure and long-term security posture. The most effective approach is to disable the finger service entirely on systems that do not require it, as the protocol is inherently insecure and provides little operational benefit in modern network environments. System administrators should implement network segmentation to prevent unauthorized access to finger service ports and consider firewall rules that block traffic on TCP port 79. Additionally, proper access control lists and authentication mechanisms should be implemented to restrict finger service access to authorized users only. Organizations should also conduct regular security audits to identify and disable unnecessary network services that pose security risks. The remediation aligns with ATT&CK technique T1083, which covers discovery of system information through network services, and represents a fundamental security principle of service minimization and least privilege access control. Regular vulnerability assessments and security configuration reviews should include checks for the presence of finger services and their accessibility to prevent exploitation of this type of information disclosure vulnerability.