CVE-2001-0080 in Catalyst 4000
Summary
by MITRE
Cisco Catalyst 6000, 5000, or 4000 switches allow remote attackers to cause a denial of service by connecting to the SSH service with a non-SSH client, which generates a protocol mismatch error.
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Analysis
by VulDB Data Team • 08/22/2024
The vulnerability identified as CVE-2001-0080 affects Cisco Catalyst 6000, 5000, and 4000 series switches that implement SSH services for remote management. This issue represents a fundamental protocol handling flaw that occurs when the switch's SSH implementation fails to properly manage connection attempts from non-compliant clients. The vulnerability resides in the SSH daemon's response mechanism when encountering malformed or non-SSH protocol connections, creating a condition where the switch becomes unresponsive to legitimate management traffic.
This vulnerability operates through a specific protocol mismatch scenario where an attacker establishes a connection to the switch's SSH port but does not properly implement the SSH protocol handshake. When the switch receives such a connection, it attempts to process the malformed data stream according to its SSH implementation, but fails to properly terminate or handle the connection state. The resulting protocol mismatch error causes the SSH service to become unresponsive, effectively rendering the switch inaccessible for legitimate administrative operations. This behavior constitutes a denial of service condition that directly impacts network availability and operational continuity.
The operational impact of this vulnerability extends beyond simple service disruption as it affects the core management capabilities of critical network infrastructure. Network administrators lose the ability to remotely manage and configure affected switches, potentially requiring physical access to restore functionality. The vulnerability affects the availability aspect of the CIA triad and can be exploited by attackers to disrupt network operations, particularly in environments where remote management is essential for maintaining network health and security posture. This type of denial of service attack can be particularly damaging in mission-critical environments where network availability is paramount.
From a cybersecurity perspective, this vulnerability demonstrates poor input validation and error handling practices in network device implementations. The issue aligns with CWE-248, which addresses "Uncaught Exception" conditions in software systems, and represents a failure to properly sanitize incoming connection attempts. The vulnerability also maps to ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through protocol manipulation. Organizations should implement network segmentation and access controls to limit exposure, while also ensuring that SSH services are properly configured with appropriate connection limits and monitoring. Regular firmware updates and security patches are essential to address such vulnerabilities, as Cisco has documented fixes for this specific issue in subsequent software releases. The vulnerability highlights the importance of robust protocol handling in network infrastructure devices and underscores the need for comprehensive security testing of management interfaces.