CVE-2000-0118 in Linux
Summary
by MITRE
The Red Hat Linux su program does not log failed password guesses if the su process is killed before it times out, which allows local attackers to conduct brute force password guessing.
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Analysis
by VulDB Data Team • 12/02/2024
The vulnerability described in CVE-2000-0118 affects the Red Hat Linux su program, which is a fundamental system utility used to switch user identities on Unix-like operating systems. This flaw represents a significant security weakness in the authentication logging mechanism that impacts the integrity of system access controls. The su command serves as a critical component in Unix security models, enabling users to escalate privileges to other accounts, particularly the root account, making proper logging of authentication attempts essential for security monitoring and threat detection.
The technical flaw occurs when the su process receives a signal that terminates it before the timeout period expires, preventing the system from recording failed password attempts in the authentication logs. This behavior creates a blind spot in the system's security monitoring capabilities because legitimate authentication attempts that are terminated prematurely do not get logged, making it impossible for administrators to detect malicious brute force attacks. The vulnerability specifically exploits the timing and signal handling aspects of the su program's execution flow, where process termination interrupts the normal logging sequence that would otherwise capture failed authentication events.
From an operational impact perspective, this vulnerability enables local attackers to conduct systematic brute force password guessing attacks without leaving detectable traces in the system logs. Attackers can repeatedly attempt to guess passwords using the su command, and when their attempts fail, they can send termination signals to the su process before it times out, effectively masking their activities from security monitoring systems. This makes the vulnerability particularly dangerous because it undermines the effectiveness of intrusion detection systems and audit trails that organizations rely on to identify unauthorized access attempts. The attack vector is straightforward and requires minimal technical expertise, making it attractive to both casual attackers and more sophisticated threat actors seeking to exploit weak authentication mechanisms.
The vulnerability aligns with CWE-613, which addresses inadequate logging of authentication attempts, and represents a specific implementation flaw in the signal handling and logging mechanisms of the su command. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through brute force methods and privilege escalation, specifically targeting the T1110.001 sub-technique for Brute Force: Password Guessing. The lack of proper logging creates an opportunity for attackers to perform reconnaissance and exploitation activities without detection, significantly weakening the security posture of affected systems. Organizations implementing this vulnerable software are essentially providing attackers with a stealthy method for conducting unauthorized access attempts while simultaneously disabling their own ability to detect such activities through standard security monitoring procedures.
The recommended mitigations include applying the appropriate security patches released by Red Hat, which would address the signal handling and logging issues in the su program. System administrators should also implement additional security measures such as account lockout policies, increased logging verbosity for authentication attempts, and monitoring for unusual patterns of process termination related to authentication utilities. Network-level protections such as fail2ban or similar intrusion prevention systems can help detect and block repeated failed authentication attempts even when the logging mechanism is compromised. Regular security audits should verify that authentication logging is functioning correctly and that no similar vulnerabilities exist in other system utilities that handle user authentication and privilege escalation.