CVE-2026-22542 in QC60
Summary
by MITRE • 01/07/2026
An attacker with access to the system's internal network can cause a denial of service on the system by making two concurrent connections through the Telnet service.
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Analysis
by VulDB Data Team • 01/07/2026
The vulnerability identified as CVE-2026-22542 represents a critical denial of service weakness within network services that utilize the Telnet protocol. This flaw specifically manifests when an attacker exploits the Telnet service by establishing two simultaneous connections to the targeted system, thereby triggering a system-wide denial of service condition that renders the service unavailable to legitimate users. The vulnerability demonstrates a fundamental flaw in the Telnet implementation's connection handling mechanism, where concurrent connection management fails to properly process multiple simultaneous sessions, leading to system instability and service disruption.
The technical root cause of this vulnerability lies in the improper handling of concurrent connections within the Telnet service daemon, which lacks adequate synchronization mechanisms to manage multiple simultaneous client sessions. When two connections are established concurrently, the service enters a state where it cannot properly allocate resources or maintain session integrity, resulting in a cascading failure that affects the entire service availability. This weakness can be categorized under CWE-400, which addresses Uncontrolled Resource Consumption, specifically focusing on the improper handling of concurrent connections leading to resource exhaustion or service failure. The vulnerability exploits a race condition in the connection processing pipeline where the service fails to properly coordinate between multiple connection requests, leading to an inconsistent state that ultimately causes the service to crash or become unresponsive.
From an operational impact perspective, this vulnerability presents a significant risk to organizations relying on Telnet services for administrative access or legacy system management. The attack vector requires only internal network access, making it particularly dangerous as it can be exploited by malicious insiders or compromised internal systems. The denial of service condition affects not just the Telnet service itself but can potentially impact the overall system stability and availability of other network services that depend on proper system resource allocation. Network administrators may experience complete loss of access to systems through Telnet, forcing reliance on alternative access methods such as SSH or physical console access, which can severely impact operational efficiency and incident response capabilities.
The threat landscape for this vulnerability aligns with ATT&CK technique T1105, which covers Remote File Copy, and T1499, which addresses Network Denial of Service, as attackers can leverage this weakness to disrupt network services without requiring extensive privileges or external access. Organizations should implement immediate mitigations including disabling Telnet services where possible and replacing them with SSH implementations, implementing connection rate limiting on Telnet ports, and establishing monitoring protocols to detect unusual connection patterns that may indicate exploitation attempts. Additionally, network segmentation strategies should be employed to limit internal access to Telnet services, and regular vulnerability assessments should be conducted to identify similar weaknesses in other network services that may exhibit comparable concurrent connection handling issues. The vulnerability underscores the importance of proper resource management and concurrent connection handling in network services, highlighting the need for robust synchronization mechanisms and comprehensive testing of service behavior under stress conditions to prevent similar weaknesses from being exploited in production environments.