CVE-2021-21565 in PowerScale OneFS
Summary
by MITRE • 08/03/2021
Dell PowerScale OneFS versions 9.1.0.3 and earlier contain a denial of service vulnerability. SmartConnect had an error condition that may be triggered to loop, using CPU and potentially preventing other SmartConnect DNS responses.
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Analysis
by VulDB Data Team • 02/20/2026
The vulnerability identified as CVE-2021-21565 affects Dell PowerScale OneFS storage systems running versions 9.1.0.3 and earlier, representing a critical denial of service weakness that impacts the SmartConnect feature. This flaw resides within the DNS resolution mechanism of the storage platform's network services, specifically within the SmartConnect component that manages DNS responses for storage cluster access. The vulnerability manifests when specific error conditions are triggered during the SmartConnect processing loop, causing the system to enter an infinite loop state that consumes excessive CPU resources. This behavior directly violates the principle of resource exhaustion protection mechanisms that should prevent single processes from monopolizing system resources and can lead to complete service unavailability for legitimate storage access requests.
The technical implementation of this vulnerability involves a programming error within the SmartConnect DNS handling code where an error condition fails to properly terminate execution flow, instead causing the system to continuously process the same error state without yielding control back to normal processing routines. This represents a classic example of a resource exhaustion attack vector where the attacker can craft specific DNS queries or network conditions that trigger the problematic code path, leading to sustained high CPU utilization that can degrade system performance or completely halt SmartConnect functionality. The vulnerability falls under CWE-835, which specifically addresses the issue of infinite loops in software implementations where loop termination conditions are not properly handled or validated.
From an operational standpoint, this vulnerability poses significant risks to enterprise storage environments that rely on SmartConnect for load balancing and failover capabilities across storage clusters. When the SmartConnect service becomes unresponsive due to this CPU looping behavior, storage clients lose access to the storage resources managed by the affected cluster, potentially causing widespread service disruption across applications and workloads dependent on those storage systems. The impact extends beyond simple availability issues as the continuous CPU consumption can affect other system services and may trigger additional system stability issues. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks that target network infrastructure components.
Organizations should implement immediate mitigations including applying the latest firmware updates from Dell that address this specific loop condition in the SmartConnect implementation. System administrators should monitor CPU utilization patterns for unusual sustained high usage on storage cluster management interfaces and implement network monitoring to detect anomalous DNS query patterns that might indicate exploitation attempts. Additionally, implementing rate limiting on DNS queries and establishing alerting mechanisms for sustained CPU spikes can help detect and respond to exploitation attempts before they cause complete service disruption. The vulnerability underscores the importance of proper input validation and error handling in network services, particularly in critical infrastructure components where denial of service can have cascading effects throughout enterprise IT operations.