CVE-2000-0579 in IRIX
Summary
by MITRE
IRIX crontab creates temporary files with predictable file names and with the umask of the user, which could allow local users to modify another user s crontab file as it is being edited.
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Analysis
by VulDB Data Team • 04/11/2019
The vulnerability described in CVE-2000-0579 represents a critical security flaw in the IRIX operating system's implementation of the crontab utility. This issue stems from the improper handling of temporary files during the crontab editing process, creating a predictable race condition that can be exploited by local attackers to gain unauthorized access to other users' scheduled tasks. The flaw specifically affects the way temporary files are created and managed within the crontab command execution environment, making it a prime example of insecure temporary file handling practices that have been documented in various security frameworks including CWE-377.
The technical implementation of this vulnerability occurs when a user invokes the crontab command to edit their scheduled tasks, causing the system to create temporary files with predictable naming conventions. These temporary files are generated with the same umask settings as the user performing the edit operation, which means that other users on the same system can potentially predict the exact file paths and manipulate the temporary files during the editing process. This predictable file naming scheme, combined with the permissive umask settings, creates an exploitable window where an attacker can substitute their own content for another user's crontab file while it is being modified, effectively allowing privilege escalation and unauthorized access to scheduled tasks.
The operational impact of this vulnerability extends beyond simple unauthorized access to crontab files, as it can enable attackers to execute malicious code with the privileges of other users. When a user's crontab contains scheduled tasks that run with elevated privileges, an attacker who gains access to that crontab file can modify it to include malicious commands or scripts. This creates a persistent backdoor mechanism that can be used to maintain access to the system or escalate privileges to higher levels of administrative control. The vulnerability is particularly concerning because it operates at the local level and can be exploited by any user on the same system, making it a significant threat to system integrity and user privacy in multi-user environments.
Security professionals should address this vulnerability through immediate system updates and patches provided by the vendor, while also implementing additional security controls to mitigate potential exploitation. The recommended mitigations include ensuring that all systems running IRIX are updated with the latest security patches, implementing proper temporary file handling practices that utilize random or unpredictable naming conventions, and configuring appropriate file permissions to prevent unauthorized access to temporary files during system operations. This vulnerability aligns with several ATT&CK techniques including privilege escalation through process injection and credential access through file system manipulation, highlighting the importance of proper file handling practices in maintaining system security. Organizations should also consider implementing monitoring solutions to detect unusual crontab file modifications and establish regular security audits to identify and remediate similar vulnerabilities in their systems. The issue demonstrates how seemingly simple file handling operations can create significant security risks when not properly implemented with security considerations in mind, emphasizing the need for secure coding practices and thorough security testing of system utilities.