CVE-2018-20871 in Grid Engine
Summary
by MITRE
In Univa Grid Engine before 8.6.3, when configured for Docker jobs and execd spooling on root_squash, weak file permissions ("other" write access) occur in certain cases (GE-6890).
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2018-20871 affects Univa Grid Engine versions prior to 8.6.3 and represents a significant security flaw in distributed computing environments that utilize Docker containerization. This issue manifests specifically when the Grid Engine is configured to handle Docker jobs with execd spooling enabled under root_squash settings, creating a dangerous permission configuration that exposes system resources to unauthorized modification.
The technical flaw stems from improper file permission handling within the Grid Engine's execution daemon component. When Docker jobs are executed with root_squash enabled, the system should enforce strict access controls to prevent unauthorized users from modifying critical system files. However, in certain scenarios, the software grants "other" write access to files that should remain protected, creating a privilege escalation vector. This weakness occurs during the spooling process where job execution files are temporarily stored, allowing malicious actors to potentially overwrite or modify these files with elevated privileges.
The operational impact of this vulnerability extends beyond simple permission issues and represents a serious threat to cluster security integrity. Attackers who can exploit this weakness may gain the ability to modify job execution scripts, inject malicious code into running containers, or manipulate the execution environment to achieve unauthorized system access. The root_squash functionality is designed to prevent users from accessing files owned by other users, but this flaw undermines that protection mechanism, potentially allowing users to escalate privileges or compromise the entire compute cluster. This vulnerability particularly affects high-performance computing environments where multiple users share resources and where containerized workloads are common.
Security professionals should note that this vulnerability aligns with CWE-732, which describes improper limitation of a privilege to other users, and can be mapped to ATT&CK technique T1068, which covers exploit for privilege escalation. Organizations utilizing Univa Grid Engine should immediately implement the patch released in version 8.6.3 to address this issue. Additional mitigations include reviewing and tightening file permissions on spool directories, implementing monitoring for unauthorized file modifications, and ensuring that only trusted users have access to the Grid Engine configuration. The vulnerability demonstrates the critical importance of proper privilege management in distributed computing systems and highlights how seemingly minor permission issues can lead to significant security breaches in complex multi-user environments.