CVE-1999-0120 in Solaris
Summary
by MITRE
sun/solaris utmp file allows local users to gain root access if it is writable by users other than root.
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Analysis
by VulDB Data Team • 04/03/2025
The vulnerability described in CVE-1999-0120 represents a critical privilege escalation flaw in sun solaris operating systems related to the utmp file permissions. This issue stems from the improper configuration of system files that track user login sessions and system activity. The utmp file serves as a crucial component in unix-like systems for maintaining information about currently logged-in users and system events, making it a prime target for malicious exploitation. When this file becomes writable by non-root users, it creates a fundamental security breach that undermines the system's integrity and access controls.
The technical flaw manifests when the utmp file lacks proper ownership and permission settings, allowing local users to modify its contents directly. This misconfiguration enables attackers to manipulate session information and potentially elevate their privileges to root level. The vulnerability operates through a classic privilege escalation vector where a local attacker with write access to the utmp file can craft malicious entries that the system subsequently interprets as legitimate root operations. The underlying mechanism exploits the trust relationship between system components and the assumption that system files maintain proper access controls. This flaw directly relates to CWE-276 which addresses incorrect permissions for critical system resources, and demonstrates how inadequate file permissions can lead to severe privilege escalation outcomes.
The operational impact of this vulnerability extends beyond simple local privilege escalation to potentially compromise entire system security post-exploitation. Once an attacker gains root access through this vector, they can manipulate system logs, install backdoors, modify critical system files, and establish persistent access. The vulnerability is particularly dangerous because it requires minimal privileges to exploit and can be leveraged by any local user who has write access to the utmp file. This makes it an attractive target for both malicious insiders and external attackers who have gained initial access to the system. The exploitability of this vulnerability aligns with ATT&CK technique T1068 which covers privilege escalation through local exploits, and T1548.1 which addresses privilege escalation through abuse of system permissions.
Effective mitigation strategies for CVE-1999-0120 require immediate attention to file permission settings and system auditing procedures. System administrators must ensure that the utmp file and related system files maintain proper ownership with root as the sole owner and restrictive permissions that prevent unauthorized modifications. The recommended approach includes implementing proper file system permissions where the utmp file should be owned by root and have permissions set to 600 or more restrictive. Regular system audits should verify that critical system files maintain appropriate access controls and that no unauthorized users have write permissions to system configuration files. Additionally, implementing proper monitoring and alerting mechanisms can help detect unauthorized modifications to system files. The remediation process should also include reviewing and hardening the overall system configuration to prevent similar issues in other system files and components. Organizations should consider implementing automated compliance checking tools that can continuously monitor for improper file permissions and alert administrators to potential security vulnerabilities.