CVE-2002-1915 in NetBSD
Summary
by MITRE
tip on multiple BSD-based operating systems allows local users to cause a denial of service (execution prevention) by using flock() to lock the /var/log/acculog file.
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Analysis
by VulDB Data Team • 07/05/2024
The vulnerability described in CVE-2002-1915 represents a significant denial of service weakness affecting multiple BSD-based operating systems through the tip daemon service. This flaw specifically targets the /var/log/acculog file which serves as a critical logging mechanism for accounting information within these systems. The tip daemon, responsible for handling terminal emulation and communication services, exhibits improper file handling behavior that creates exploitable conditions for local attackers. The vulnerability stems from the daemon's failure to properly manage file locks and access permissions, particularly when attempting to acquire exclusive locks on the accounting log file. This issue manifests when a local user employs the flock() system call to lock the designated log file, thereby preventing the tip daemon from executing its normal operations and effectively causing a system-wide denial of service condition.
The technical implementation of this vulnerability involves the exploitation of a race condition or improper resource management within the tip daemon's file access routines. When the daemon attempts to write to or read from the /var/log/acculog file, it relies on proper file locking mechanisms to ensure data integrity and concurrent access control. However, the flaw allows local users to manipulate the locking state of this critical file through direct system calls, specifically the flock() function which provides advisory locking capabilities. This manipulation creates a scenario where the daemon cannot obtain the necessary file locks to perform its logging operations, leading to execution failures and system service disruption. The vulnerability demonstrates poor adherence to secure coding practices and highlights the importance of proper resource management in system-level services. According to CWE guidelines, this represents a weakness in resource management where the system fails to properly handle file access controls and locking mechanisms.
The operational impact of CVE-2002-1915 extends beyond simple service interruption to potentially compromise system availability and stability. Local users with minimal privileges can exploit this vulnerability to systematically prevent the tip daemon from functioning, which may affect terminal services, remote access capabilities, and overall system logging integrity. The denial of service condition can persist until the affected daemon is manually restarted or the system is rebooted, creating potential operational disruptions for system administrators. In environments where terminal services are heavily utilized, this vulnerability could provide attackers with a persistent method for service degradation. The attack vector is particularly concerning because it requires only local access and basic system call knowledge, making it easily exploitable by users with minimal privileges. This aligns with ATT&CK techniques focusing on privilege escalation and denial of service operations.
Mitigation strategies for this vulnerability should focus on both immediate operational fixes and long-term architectural improvements. System administrators should implement proper file access controls and ensure that the tip daemon runs with minimal necessary privileges to reduce the impact of such attacks. The most effective immediate solution involves modifying the daemon's file handling routines to properly check for and handle file locking states, ensuring that the service can gracefully recover from lock contention scenarios. Additionally, implementing proper logging mechanisms that can detect and alert on unusual file access patterns would help identify exploitation attempts. Regular system updates and security patches should be applied immediately to address the underlying implementation flaws in the tip daemon. Security monitoring should include checks for unauthorized file locking operations on critical system files, particularly those used for accounting and logging purposes. The vulnerability serves as a reminder of the critical importance of secure file handling practices in system services and the need for proper resource management in multi-user environments. Organizations should also consider implementing automated monitoring solutions that can detect and respond to file access anomalies that may indicate exploitation attempts.