CVE-2001-0559 in Cron
Summary
by MITRE
crontab in Vixie cron 3.0.1 and earlier does not properly drop privileges after the failed parsing of a modification operation, which could allow a local attacker to gain additional privileges when an editor is called to correct the error.
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Analysis
by VulDB Data Team • 11/17/2024
The vulnerability identified as CVE-2001-0559 resides within the Vixie cron 3.0.1 and earlier versions where the crontab utility fails to properly drop privileges following a failed parsing operation. This flaw specifically manifests when cron encounters a malformed modification operation and subsequently invokes an editor to correct the error. The technical implementation of this vulnerability stems from improper privilege management during error recovery processes, creating a window where elevated privileges remain active despite the system attempting to handle parsing failures. The flaw represents a classic privilege escalation issue where the system does not adequately enforce the principle of least privilege during error handling, allowing malicious actors to exploit this gap in privilege management.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a mechanism to execute arbitrary code with elevated privileges. When cron attempts to parse a malformed crontab entry and calls an editor to correct the error, the system maintains root privileges during this critical phase. This creates an opportunity for local attackers to manipulate the environment in such a way that the editor process inherits these elevated privileges, potentially allowing the execution of malicious commands or the modification of system files. The vulnerability is particularly concerning because it operates within the legitimate system administration workflow, making it difficult to detect through normal monitoring procedures. This issue directly aligns with CWE-276, which addresses improper privilege management, and can be mapped to ATT&CK technique T1068, which covers privilege escalation through the exploitation of system vulnerabilities.
Mitigation strategies for CVE-2001-0559 should focus on immediate patching of affected Vixie cron installations to versions that properly implement privilege dropping mechanisms. System administrators must ensure that all cron installations are updated to versions that correctly handle privilege management during error recovery operations. Additionally, organizations should implement strict access controls and monitoring around crontab modification processes to detect unauthorized changes or suspicious privilege escalation attempts. The recommended approach includes configuring cron to run with minimal necessary privileges and ensuring that any editor invoked during error recovery operates with reduced privileges. Security controls should also include regular audits of crontab entries and monitoring for unauthorized modifications to system scheduling files. Organizations should consider implementing additional layers of protection such as file integrity monitoring solutions that can detect changes to cron-related binaries or configuration files, thereby providing early warning of potential exploitation attempts. The vulnerability demonstrates the critical importance of proper privilege management in system utilities and highlights the need for comprehensive security testing of error handling procedures in critical system components.