CVE-2020-3200 in IOS
Summary
by MITRE
A vulnerability in the Secure Shell (SSH) server code of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. The vulnerability is due to an internal state not being represented correctly in the SSH state machine, which leads to an unexpected behavior. An attacker could exploit this vulnerability by creating an SSH connection to an affected device and using a specific traffic pattern that causes an error condition within that connection. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 10/21/2020
The vulnerability identified as CVE-2020-3200 represents a critical flaw in the Secure Shell server implementation within Cisco IOS and IOS XE software platforms. This issue stems from an improper handling of internal state management within the SSH protocol state machine, creating a condition where specific traffic patterns can trigger unexpected device behavior. The vulnerability affects network devices that rely on SSH for remote management and administrative access, potentially compromising the availability of critical network infrastructure. The flaw demonstrates a fundamental weakness in how the software handles session state transitions during SSH communication, which directly impacts the stability and reliability of affected network equipment.
The technical exploitation of this vulnerability requires an authenticated attacker who can establish an SSH connection to the targeted device and then manipulate traffic patterns to force an error condition within the SSH state machine. This specific error condition manifests as an unexpected device reload, effectively causing a denial of service attack against the network infrastructure. The vulnerability operates at the protocol level within the SSH server implementation, where the internal state representation fails to properly account for certain connection scenarios, leading to cascading failures that result in system restarts. The attack vector is particularly concerning because it requires only authentication credentials to establish the initial connection, making it accessible to attackers who have gained legitimate access to the device or who can exploit weak authentication mechanisms.
The operational impact of CVE-2020-3200 extends beyond simple service disruption, as network administrators face the challenge of maintaining availability for critical infrastructure components that may experience unexpected reloads. This vulnerability directly impacts the CIA triad, specifically affecting availability by enabling denial of service conditions that can compromise network operations and potentially disrupt business continuity. The consequences include service interruptions, potential data loss from unexpected restarts, and increased administrative overhead as IT teams must respond to and recover from these unexpected device reloads. Organizations relying on Cisco network equipment for core infrastructure services face significant risk, as these reloads can occur without warning and may affect multiple network services simultaneously.
Mitigation strategies for CVE-2020-3200 should focus on both immediate patching and operational controls to reduce risk exposure. Cisco has released software updates addressing this vulnerability, and organizations should prioritize applying these patches to affected devices as soon as possible. Network administrators should implement strict access controls and monitoring to detect unauthorized SSH connections that could indicate exploitation attempts. The vulnerability aligns with CWE-284 (Improper Access Control) and CWE-691 (Insufficient Control Flow Management) categories, indicating weaknesses in both access control mechanisms and state management within the software. From an ATT&CK framework perspective, this vulnerability maps to T1072 (Software Deployment Tools) and T1499 (Endpoint Termination) tactics, as it enables attackers to disrupt endpoint services through legitimate administrative protocols. Organizations should also consider implementing network segmentation and monitoring solutions to detect anomalous SSH traffic patterns that could indicate exploitation attempts.