CVE-2002-0754 in FreeBSD
Summary
by MITRE
Kerberos 5 su (k5su) in FreeBSD 4.4 and earlier relies on the getlogin system call to determine if the user running k5su is root, which could allow a root-initiated process to regain its privileges after it has dropped them.
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Analysis
by VulDB Data Team • 06/23/2024
The vulnerability identified as CVE-2002-0754 affects Kerberos 5 su (k5su) functionality in FreeBSD versions 4.4 and earlier, representing a critical privilege escalation flaw that exploits the trust relationship between system calls and user identity verification. This issue stems from the k5su utility's improper handling of privilege dropping mechanisms, where the system relies on the getlogin system call to verify root status. The fundamental flaw lies in the assumption that getlogin will consistently return accurate user identification information, which becomes problematic when a process has already dropped its privileges. When a root-initiated process executes k5su and subsequently drops privileges, the utility fails to properly validate the user context, creating a potential pathway for privilege escalation attacks. The vulnerability specifically targets the privilege management architecture of the Kerberos authentication system, where proper privilege separation is essential for maintaining system security boundaries.
The technical exploitation of this vulnerability occurs through a carefully crafted sequence of operations that leverages the inherent weakness in the getlogin system call implementation. When k5su executes, it initially runs with root privileges but then attempts to drop these privileges to operate under a different user context. However, the utility's reliance on getlogin for root verification creates a race condition or context confusion scenario. Attackers can manipulate the environment in such a way that the getlogin system call returns incorrect information, allowing the process to believe it is operating as root even when it has dropped privileges. This misidentification enables the malicious process to bypass intended security controls and potentially regain root access. The vulnerability demonstrates poor adherence to secure coding practices and highlights the importance of proper privilege management in security-critical applications, aligning with CWE-276 which addresses improper privileges and CWE-284 which covers inadequate access control mechanisms.
The operational impact of CVE-2002-0754 extends beyond simple privilege escalation, as it fundamentally undermines the security model of systems relying on Kerberos authentication and privilege management. This vulnerability enables attackers to bypass the intended security controls that separate user contexts and protect system resources from unauthorized access. Once exploited, the vulnerability allows for complete system compromise, as attackers can execute arbitrary code with root privileges and potentially gain access to all system resources. The impact is particularly severe in environments where Kerberos authentication is heavily used, such as enterprise networks, academic institutions, and systems requiring robust authentication mechanisms. The vulnerability affects the core authentication and authorization infrastructure, potentially enabling attackers to establish persistent access, modify system files, install malware, or exfiltrate sensitive data. Organizations using affected FreeBSD versions face significant risk of unauthorized system access and potential data breaches.
Mitigation strategies for CVE-2002-0754 require immediate system updates and configuration changes to address the underlying privilege management flaw. The most effective solution involves upgrading to FreeBSD versions that contain patches addressing this specific vulnerability, as the original implementation cannot be reliably secured through configuration changes alone. System administrators should implement the latest security patches from FreeBSD, which typically include modifications to how k5su handles privilege verification and user context management. Additionally, organizations should consider implementing additional security controls such as mandatory access controls, privilege separation mechanisms, and monitoring for suspicious process behavior. The mitigation approach should align with defensive security principles and address the root cause rather than attempting to work around the flawed implementation. Security teams should also conduct thorough vulnerability assessments to identify systems running affected FreeBSD versions and ensure proper patch management procedures are in place to prevent similar issues in the future, reflecting best practices from the ATT&CK framework's privilege escalation techniques and the broader security community's recommendations for secure system administration.