CVE-2016-7498 in Compute
Summary
by MITRE
OpenStack Compute (nova) 13.0.0 does not properly delete instances from compute nodes, which allows remote authenticated users to cause a denial of service (disk consumption) by deleting instances while in the resize state. NOTE: this vulnerability exists because of a CVE-2015-3280 regression.
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Analysis
by VulDB Data Team • 04/27/2019
The vulnerability identified as CVE-2016-7498 affects OpenStack Compute (nova) version 13.0.0 and represents a significant denial of service weakness that stems from a regression introduced in CVE-2015-3280. This flaw manifests when the system fails to properly remove instances from compute nodes, creating a persistent state where deleted instances continue to consume system resources. The vulnerability specifically impacts the resize operation within the nova service, where instance deletion attempts during the resize process result in incomplete cleanup operations. This regression essentially undermines the proper resource management mechanisms that should occur when instances are removed from the system, leading to a gradual accumulation of orphaned resources that consume disk space and other computational assets.
The technical implementation of this vulnerability exploits the improper handling of instance lifecycle management within the nova compute service. When a user attempts to delete an instance that is currently in the resize state, the system fails to completely purge all associated metadata, storage allocations, and resource references. This incomplete cleanup process creates a scenario where the system continues to track and maintain references to the deleted instance even though it no longer exists in the operational state. The flaw operates at the core of OpenStack's resource management architecture, specifically targeting the interaction between the nova scheduler, compute nodes, and the underlying storage systems that manage instance data. The vulnerability's persistence is particularly concerning as it allows attackers to repeatedly perform deletion operations during resize states, causing progressive disk consumption that can eventually exhaust available storage capacity.
From an operational impact perspective, this vulnerability creates a sustained denial of service condition that can severely degrade system performance and availability. The continuous disk consumption caused by improperly deleted instances leads to reduced storage capacity for legitimate operations, potentially causing cascading failures throughout the OpenStack environment. Attackers can exploit this weakness by repeatedly initiating instance deletion requests during resize operations, creating a resource exhaustion scenario that affects not only the targeted compute nodes but also impacts the overall stability of the cloud infrastructure. The vulnerability's authentication requirement means that only authorized users can exploit this weakness, but the impact can be significant given that legitimate users may inadvertently trigger the condition or malicious actors with valid credentials can intentionally cause the resource consumption. This weakness directly maps to CWE-400, which describes improper resource cleanup or resource leak conditions in software systems.
The mitigation strategies for CVE-2016-7498 require both immediate patching and operational monitoring to address the regression introduced in CVE-2015-3280. Organizations should prioritize updating their OpenStack deployments to versions that contain fixes for both vulnerabilities, ensuring that the proper instance deletion logic is restored and that the resize state handling properly cleans up all associated resources. System administrators must implement monitoring solutions that track disk usage patterns and identify unusual consumption spikes that may indicate the presence of this vulnerability. Additionally, implementing automated resource cleanup processes and regular audits of instance states can help detect and remediate affected systems before they reach critical resource exhaustion levels. The vulnerability's relationship to the ATT&CK framework's resource exhaustion tactics highlights the importance of implementing proper access controls and monitoring to prevent both accidental and intentional exploitation of this weakness. Organizations should also consider implementing rate limiting and resource quotas to limit the potential impact of this vulnerability while patches are being deployed across their infrastructure.