CVE-2001-0560 in Cron
Summary
by MITRE
Buffer overflow in Vixie cron 3.0.1-56 and earlier could allow a local attacker to gain additional privileges via a long username (> 20 characters).
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Analysis
by VulDB Data Team • 04/30/2019
The vulnerability identified as CVE-2001-0560 represents a critical buffer overflow flaw in Vixie cron version 3.0.1-56 and earlier implementations. This issue specifically affects the cron daemon's handling of user names during job scheduling operations, creating a pathway for local attackers to escalate their privileges within the system. The vulnerability stems from inadequate input validation mechanisms that fail to properly check the length of user identifiers before processing them in memory buffers.
The technical flaw manifests when a user attempts to schedule a cron job using a username exceeding twenty characters in length. The cron daemon's internal buffer allocation does not account for this extended input, causing data to overflow into adjacent memory regions. This buffer overflow condition creates opportunities for attackers to overwrite critical memory segments including return addresses, function pointers, or other control data structures. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which directly enables privilege escalation attacks by allowing malicious code execution with elevated privileges.
Operationally, this vulnerability poses significant risks to system security as it requires only local access to exploit effectively. An attacker with basic user privileges can leverage this flaw to execute arbitrary code with the privileges of the cron daemon, typically running with root-level permissions. The impact extends beyond simple privilege escalation, potentially enabling attackers to gain persistent access, modify system files, or establish backdoors within the compromised system. This makes the vulnerability particularly dangerous in multi-user environments where cron jobs are frequently utilized for automated tasks and system maintenance operations.
The exploitation of this vulnerability aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation" and T1059 which covers "Command and Scripting Interpreter" as attackers can leverage the compromised cron service to execute malicious commands. Organizations should implement immediate mitigations including upgrading to patched versions of Vixie cron, applying security patches, and monitoring for suspicious cron job activities. System administrators should also consider implementing additional controls such as restricting cron access permissions, monitoring user account creation, and establishing robust input validation procedures. The vulnerability highlights the importance of proper buffer management and input validation in system-level software components, particularly those handling user-provided data in privileged contexts.