CVE-2014-8994 in Check Diskio
Summary
by MITRE
The check_diskio plugin 3.2.6 and earlier for Nagios and Icinga allows local users to write to arbitrary files via a symlink attack on a temporary file with a predictable name (tmp/check_diskio_status-*-*).
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Analysis
by VulDB Data Team • 04/06/2018
The vulnerability identified as CVE-2014-8994 affects the check_diskio plugin version 3.2.6 and earlier implementations within Nagios and Icinga monitoring systems. This issue represents a classic symlink attack scenario that exploits predictable temporary file naming conventions to enable unauthorized file system modifications. The vulnerability specifically targets the temporary file creation process where the plugin generates files with names following the pattern tmp/check_diskio_status-- which can be easily anticipated by local attackers.
The technical flaw stems from the plugin's insufficient handling of temporary file creation processes, where it creates temporary files with predictable names without proper security checks or atomic file creation mechanisms. When a local user can predict the temporary file name, they can establish a symbolic link with that name before the legitimate plugin process creates the actual file. This allows the attacker to redirect the plugin's write operations to arbitrary locations on the file system, potentially enabling privilege escalation or data manipulation attacks. The vulnerability is classified as a race condition in file system operations where the timing window between symlink creation and file access provides the attack vector.
The operational impact of this vulnerability extends beyond simple file system manipulation as it can be leveraged to compromise the integrity of monitoring data and potentially escalate privileges within the monitoring environment. Since Nagios and Icinga systems often run with elevated privileges to monitor system resources effectively, an attacker who successfully exploits this vulnerability could gain unauthorized access to sensitive monitoring data or manipulate system alerts. This type of attack directly violates the principle of least privilege and can lead to complete compromise of the monitoring infrastructure. The attack requires local system access but can result in significant security implications for organizations relying on these monitoring tools.
Mitigation strategies for this vulnerability include immediate patching of the check_diskio plugin to version 3.2.7 or later where the issue has been resolved through proper temporary file handling mechanisms. Organizations should implement proper file system permissions and ensure that temporary directories have restrictive access controls to prevent unauthorized symlink creation. The solution involves using atomic file creation methods that prevent race conditions, such as creating temporary files with random names or using system functions that guarantee exclusive file creation. This vulnerability aligns with CWE-367 which addresses time-of-check to time-of-use (TOCTOU) race conditions and represents a clear violation of the ATT&CK technique T1059.007 for execution through command-line interfaces. System administrators should also implement monitoring for suspicious symlink creation patterns and conduct regular security audits of monitoring tool configurations to prevent similar issues in other components of the infrastructure.