CVE-2001-0036 in Kerberos
Summary
by MITRE
KTH Kerberos IV allows local users to overwrite arbitrary files via a symlink attack on a ticket file.
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Analysis
by VulDB Data Team • 05/29/2018
The vulnerability identified as CVE-2001-0036 resides within the KTH Kerberos IV implementation, a widely deployed authentication system that has been foundational to network security infrastructure for decades. This flaw represents a classic symlink attack vector that exploits the insecure handling of temporary files during authentication processes. The vulnerability specifically targets the ticket file creation mechanism where the system fails to properly validate file paths, creating an opportunity for local attackers to manipulate the file system through symbolic link manipulation. The issue manifests when Kerberos IV generates ticket files in predictable locations without adequate security checks to prevent unauthorized file overwrites.
The technical exploitation of this vulnerability occurs through a carefully crafted symlink attack that leverages the predictable naming conventions of ticket files within the Kerberos IV framework. When a user authenticates, the system creates ticket files in temporary directories without proper validation of the symbolic link status of parent directories. Attackers can place malicious symbolic links in the path where ticket files are expected to be created, causing the system to write sensitive data to locations controlled by the attacker rather than the intended destination. This represents a fundamental flaw in file system access control and privilege separation mechanisms, allowing local users with minimal privileges to escalate their access and potentially overwrite critical system files or configuration data. The vulnerability maps directly to CWE-59 and CWE-367, which address improper file handling and symlink attacks respectively, demonstrating a clear violation of secure file system operations principles.
The operational impact of this vulnerability extends beyond simple file overwrites to potentially compromise entire authentication systems and create persistent backdoors within networked environments. Local attackers can exploit this weakness to replace legitimate ticket files with malicious content, potentially enabling them to impersonate users or gain elevated privileges within the Kerberos domain. The attack requires only local access to the system, making it particularly dangerous as it can be executed by any user with basic system privileges. Network security administrators face significant challenges in detecting such attacks since they occur within the local file system context and may not generate obvious network traffic patterns. This vulnerability can be leveraged to establish persistent access points, modify authentication configurations, or create unauthorized access to protected resources within the Kerberos infrastructure.
Mitigation strategies for CVE-2001-0036 require immediate implementation of proper file system access controls and secure temporary file handling practices. Organizations should implement strict file permission controls on temporary directories used by Kerberos IV, ensuring that symbolic link resolution is disabled or properly validated before file creation operations. The recommended approach involves modifying the Kerberos IV implementation to use atomic file creation methods that prevent symlink attacks, such as creating files with exclusive access modes or using secure temporary file generation libraries. System administrators should also conduct thorough security audits to identify and remove existing symbolic links in critical directories, while implementing monitoring solutions to detect suspicious file system activities. The solution aligns with ATT&CK technique T1548.001 for privilege escalation through file system manipulation and emphasizes the importance of following secure coding practices as outlined in NIST SP 800-160 and OWASP Top Ten security guidelines. Additionally, upgrading to more modern authentication systems that have addressed these fundamental security flaws provides the most comprehensive long-term protection against similar vulnerabilities.