CVE-2000-0972 in HP-UX
Summary
by MITRE
HP-UX 11.00 crontab allows local users to read arbitrary files via the -e option by creating a symlink to the target file during the crontab session, quitting the session, and reading the error messages that crontab generates.
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Analysis
by VulDB Data Team • 09/30/2024
The vulnerability described in CVE-2000-0972 represents a significant privilege escalation and information disclosure issue affecting HP-UX 11.00 systems. This flaw resides within the crontab utility implementation and exploits a fundamental race condition in how the system handles file operations during cron job management sessions. The vulnerability specifically targets the -e option of crontab which is designed to edit existing cron jobs, but due to improper file handling mechanisms, it creates opportunities for malicious local users to access files they should not normally be able to read. The flaw demonstrates a classic case of insecure temporary file handling that has been documented in various security frameworks including CWE-377 and CWE-378, where the system creates temporary files with predictable names or locations that can be manipulated by unauthorized users.
The technical exploitation mechanism relies on a carefully orchestrated sequence of file system operations that takes advantage of the timing window between when crontab creates temporary files and when it processes them. During a crontab session, the system creates temporary files to store the cron job definitions being edited, but these temporary files are not properly secured against symbolic link attacks. An attacker can create a symbolic link with the same name as the temporary file that crontab will use, pointing to a sensitive file such as /etc/shadow or /etc/passwd. When crontab executes and attempts to access the temporary file, it follows the symbolic link and inadvertently exposes the contents of the target file through error messages generated during the session. This technique is particularly effective because the error messages contain the file contents, allowing attackers to extract sensitive information without directly reading the files through normal system calls.
The operational impact of this vulnerability extends beyond simple information disclosure to include potential privilege escalation scenarios that could compromise the entire system. Local users who can execute crontab commands gain the ability to read files that are typically protected by system permissions, potentially exposing passwords, cryptographic keys, and other sensitive system information. This vulnerability directly relates to the ATT&CK framework's technique T1003 - OS Credential Dumping, where adversaries seek to obtain credentials from system files, and T1059 - Command and Scripting Interpreter, where attackers leverage system utilities to execute malicious operations. The vulnerability affects systems where users have basic shell access and can execute crontab commands, making it particularly dangerous in multi-user environments where system administrators may not properly monitor user activities.
Mitigation strategies for this vulnerability require both immediate system-level patches and operational security improvements. The most effective solution involves applying the appropriate HP-UX security patches that address the race condition in crontab's temporary file handling mechanisms. System administrators should also implement proper file system permissions and ensure that temporary directories used by crontab are properly secured with restrictive permissions that prevent symbolic link creation by unauthorized users. Additionally, monitoring and logging of crontab usage should be enhanced to detect suspicious activities, particularly around the creation of symbolic links in temporary directories. The vulnerability highlights the importance of following secure coding practices and implementing proper input validation, as outlined in OWASP Top 10 and NIST guidelines for secure software development. Organizations should also consider implementing privilege separation techniques and regularly auditing system configurations to prevent similar issues in other system utilities that may be vulnerable to the same class of race condition attacks.