CVE-2001-0364 in SSH
Summary
by MITRE
SSH Communications Security sshd 2.4 for Windows allows remote attackers to create a denial of service via a large number of simultaneous connections.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability identified as CVE-2001-0364 affects SSH Communications Security sshd version 2.4 running on Windows systems, representing a significant denial of service weakness that can be exploited by remote attackers. This flaw specifically targets the sshd daemon's handling of concurrent connection requests, creating a scenario where malicious actors can overwhelm the service through massive connection attempts. The vulnerability stems from insufficient resource management and connection handling mechanisms within the sshd implementation, particularly in its Windows-specific codebase. According to CWE-400, this represents a classic resource exhaustion vulnerability where the system's ability to manage concurrent connections becomes compromised, leading to service unavailability for legitimate users. The attack vector involves sending a large volume of simultaneous connection requests to the sshd service, which can cause the daemon to consume excessive system resources or crash entirely.
The technical implementation of this vulnerability exploits the sshd daemon's inability to properly throttle or manage concurrent connection attempts within the Windows environment. When multiple connection requests are processed simultaneously, the service fails to maintain proper resource allocation and connection state management, leading to a cascading failure that can render the SSH service completely unavailable. This behavior aligns with ATT&CK technique T1499.004, which describes network denial of service attacks targeting remote services. The flaw demonstrates poor input validation and resource management practices in the sshd implementation, where the system does not adequately implement connection rate limiting or resource consumption controls. The Windows-specific nature of the vulnerability suggests that the underlying Windows socket handling or threading mechanisms may not be properly coordinated with the sshd's connection management logic, creating a point of failure that can be easily exploited by attackers with minimal resources.
The operational impact of this vulnerability extends beyond simple service disruption, potentially affecting critical infrastructure that relies on SSH for remote administration and secure communications. Organizations running sshd 2.4 on Windows systems face the risk of unauthorized service disruption that can compromise business continuity and system availability. The vulnerability's remote exploitation capability means that attackers do not require physical access or local network presence to cause significant damage, making it particularly dangerous in enterprise environments where SSH services are commonly used for administrative access. This weakness can be leveraged as part of broader attack campaigns where denial of service serves as a precursor to more sophisticated exploitation attempts, as outlined in the ATT&CK framework's approach to service disruption as a tactical objective. The impact is particularly severe because SSH is often considered a critical administrative service, and its disruption can cascade to affect other network services and systems that depend on secure remote access capabilities.
Mitigation strategies for this vulnerability should focus on immediate patching of the sshd daemon to version 2.5 or later, which includes proper connection handling and resource management improvements. Network-level protections such as implementing connection rate limiting, using firewalls to restrict SSH access to trusted IP ranges, and deploying intrusion detection systems can provide additional defense layers. System administrators should also implement monitoring solutions to detect unusual connection patterns that may indicate exploitation attempts. The fix addresses the underlying resource exhaustion issue by implementing proper connection queuing and resource allocation mechanisms that prevent the daemon from being overwhelmed by simultaneous connection attempts. Organizations should also consider implementing SSH access controls that limit the number of concurrent connections per user or host, as recommended by industry best practices for secure remote access management. Additionally, regular security assessments and vulnerability scanning should be conducted to identify and remediate similar issues in other network services and systems that may exhibit comparable resource management weaknesses.