CVE-2001-0235 in crontab
Summary
by MITRE
Vulnerability in crontab allows local users to read crontab files of other users by replacing the temporary file that is being edited while crontab is running.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability described in CVE-2001-0235 represents a classic race condition flaw in the crontab utility that affects unix-like operating systems. This issue resides in the way the crontab command handles temporary files during the editing process, creating a window of opportunity for malicious local users to exploit the system. The vulnerability specifically targets the temporary file creation and management mechanism that occurs when users attempt to modify their crontab entries through the standard crontab interface.
The technical implementation of this flaw stems from the crontab utility's approach to file handling where it creates a temporary file to store user modifications before applying them to the actual crontab. During this process, the temporary file is created with predictable naming conventions and insufficient permissions, allowing local users to replace the temporary file with a symbolic link pointing to another user's crontab file. This race condition occurs between the time the temporary file is created and when the system validates or processes it, enabling unauthorized access to sensitive scheduling information.
From an operational impact perspective, this vulnerability exposes critical system security controls by allowing local privilege escalation and information disclosure. Attackers can access other users' crontab files which typically contain scheduled tasks, automated commands, and potentially sensitive execution patterns. The implications extend beyond simple information gathering as these files may contain credentials, system access patterns, or scheduled administrative tasks that could be leveraged for further compromise. The vulnerability affects the principle of least privilege by enabling unauthorized access to system scheduling information that should remain private to individual users.
The flaw aligns with CWE-362, which specifically addresses race conditions in software systems where the order of operations creates security vulnerabilities. This weakness demonstrates poor file handling practices and inadequate synchronization mechanisms during file operations. The vulnerability also maps to ATT&CK technique T1059.007, which involves the use of scheduled tasks or cron jobs as a method of execution or persistence, though in this case the attack vector targets information disclosure rather than execution. Organizations implementing this flawed crontab functionality face significant risk of unauthorized access to system scheduling information and potential escalation of privileges through the exposure of automated tasks.
Mitigation strategies for this vulnerability require immediate system updates and patches that address the race condition in temporary file handling. The recommended approach involves implementing proper file permission controls, using atomic file operations, and ensuring that temporary files are created with unique names and appropriate access restrictions. System administrators should also consider implementing additional monitoring for crontab file modifications and establishing proper access controls that prevent unauthorized users from accessing other users' scheduling information. The fix typically involves modifying the crontab utility to use more secure temporary file creation methods that eliminate the race condition window.