CVE-2018-14660 in GlusterFS
Summary
by MITRE
A flaw was found in glusterfs server through versions 4.1.4 and 3.1.2 which allowed repeated usage of GF_META_LOCK_KEY xattr. A remote, authenticated attacker could use this flaw to create multiple locks for single inode by using setxattr repetitively resulting in memory exhaustion of glusterfs server node.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2018-14660 represents a critical memory exhaustion flaw within the GlusterFS distributed file system implementation. This issue affects versions 4.1.4 and 3.1.2 of the GlusterFS server software, where a specific weakness in the handling of extended attributes allows for improper resource management. The flaw specifically targets the GF_META_LOCK_KEY xattr mechanism, which is designed to manage metadata locking operations within the file system. When an authenticated remote attacker exploits this vulnerability, they can repeatedly invoke the setxattr system call to create multiple lock entries for a single inode, effectively bypassing normal resource allocation limits and consuming excessive memory resources on the target server node.
The technical implementation of this vulnerability stems from inadequate validation and resource management within the GlusterFS server's extended attribute handling subsystem. The GF_META_LOCK_KEY xattr serves as a metadata locking mechanism to prevent concurrent modifications to file system objects, but the implementation fails to properly track or limit the number of lock instances that can be created for a single inode. This allows an attacker to continuously submit setxattr requests with the same key, creating an unbounded growth of lock structures in memory. Each repeated invocation consumes additional memory resources without proper cleanup or rate limiting, leading to progressive memory exhaustion that can ultimately cause the server process to crash or become unresponsive. This type of vulnerability falls under CWE-400, which specifically addresses Uncontrolled Resource Consumption, and represents a classic denial of service scenario where legitimate system resources are consumed by malicious activity.
The operational impact of CVE-2018-14660 extends beyond simple service disruption to potentially compromise the entire file system availability and stability. When the GlusterFS server node experiences memory exhaustion due to this vulnerability, it can result in complete service unavailability for all clients connected to that storage node. The affected system may exhibit symptoms including gradual performance degradation, complete system hang, or forced process termination, all of which severely impact business continuity and data access availability. In large-scale deployments where GlusterFS serves as a primary storage backend for critical applications, this vulnerability could lead to cascading failures affecting multiple dependent services and applications. The authenticated nature of the attack means that only users with valid credentials can exploit this flaw, but this still represents a significant risk in environments where credential compromise or insider threats are possible, as the attacker would have legitimate access rights to perform the exploitation.
Mitigation strategies for CVE-2018-14660 should focus on both immediate patching and operational controls to prevent exploitation. The primary solution involves upgrading to patched versions of GlusterFS that properly implement resource limits and validation for extended attribute operations, specifically addressing the improper handling of GF_META_LOCK_KEY xattr usage. Organizations should implement monitoring solutions that track memory consumption patterns and extended attribute usage on GlusterFS servers to detect anomalous behavior indicative of exploitation attempts. Network-level controls can be implemented to limit the rate of setxattr operations from individual authenticated users or applications, providing additional defense-in-depth measures. Additionally, system administrators should consider implementing resource limits and process monitoring to detect and automatically terminate processes that exhibit abnormal memory consumption patterns. The vulnerability demonstrates the importance of proper resource management in distributed file systems and highlights the need for comprehensive testing of extended attribute handling mechanisms against potential abuse scenarios. This issue also aligns with ATT&CK technique T1499.001, which covers Network Denial of Service, as the exploitation results in service unavailability through resource exhaustion. Organizations should also review their access control policies to ensure that only authorized users have the necessary privileges to perform extended attribute operations, reducing the potential attack surface for this specific vulnerability.