CVE-2019-1806 in Small Business Sx200
Summary
by MITRE
A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco Small Business Sx200, Sx300, Sx500, ESW2 Series Managed Switches and Small Business Sx250, Sx350, Sx550 Series Switches could allow an authenticated, remote attacker to cause the SNMP application of an affected device to cease processing traffic, resulting in the CPU utilization reaching one hundred percent. Manual intervention may be required before a device resumes normal operations. The vulnerability is due to improper validation of SNMP protocol data units (PDUs) in SNMP packets. An attacker could exploit this vulnerability by sending a malicious SNMP packet to an affected device. A successful exploit could allow the attacker to cause the device to cease forwarding traffic, which could result in a denial of service (DoS) condition. Cisco has released firmware updates that address this vulnerability.
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability identified as CVE-2019-1806 represents a critical denial of service weakness within Cisco's Small Business switching portfolio, specifically affecting models including the Sx200, Sx300, Sx500, ESW2 Series, and Sx250, Sx350, Sx550 Series switches. This flaw resides in the Simple Network Management Protocol input packet processor, which serves as a fundamental component for network monitoring and management operations. The affected devices operate under the assumption that incoming SNMP packets contain valid protocol data units, creating an exploitable gap in input validation mechanisms that directly impacts system stability and operational continuity. The vulnerability manifests when these switches process malformed SNMP packets that contain improperly structured PDUs, leading to a cascading failure in the SNMP application's ability to maintain normal traffic processing functions.
The technical exploitation of CVE-2019-1806 occurs through a specific protocol validation failure that enables authenticated remote attackers to manipulate the SNMP service without requiring elevated privileges. This vulnerability maps directly to CWE-20, which describes improper input validation, and demonstrates how insufficient sanitization of network protocol data can lead to system instability. Attackers can craft malicious SNMP packets that trigger a condition where the affected device's CPU utilization spikes to 100 percent, effectively causing the switch to become unresponsive to legitimate network traffic. The root cause lies in the failure to properly validate SNMP PDUs before processing, allowing malformed data to propagate through the system's SNMP input handlers and ultimately consume all available CPU resources. This type of exploitation aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting network infrastructure components.
The operational impact of this vulnerability extends beyond simple service disruption, as it fundamentally compromises the network infrastructure's reliability and availability. When the SNMP application ceases processing traffic, the switch effectively becomes a network black hole, unable to forward legitimate packets while simultaneously consuming all available processing capacity. Network administrators face the prospect of manual intervention requirements to restore normal operations, creating potential downtime windows that can significantly impact business continuity and network performance. The vulnerability affects devices that are commonly deployed in small business environments where network monitoring is critical, making the denial of service condition particularly disruptive. The affected switches are designed for environments where continuous network availability is essential, and this vulnerability undermines that fundamental expectation by creating conditions where network operations can be rendered completely inoperative. Cisco's release of firmware updates represents the primary mitigation strategy, addressing the input validation gap by implementing proper SNMP PDU validation mechanisms that prevent malformed packets from causing system resource exhaustion and maintain the switches' ability to process legitimate network traffic without interruption.