CVE-2018-0291 in NX-OS
Summary
by MITRE
A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco NX-OS Software could allow an authenticated, remote attacker to cause the SNMP application on an affected device to restart unexpectedly. 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 crafted SNMP packet to an affected device. A successful exploit could allow the attacker to cause the SNMP application to restart multiple times, leading to a system-level restart and a denial of service (DoS) condition. This vulnerability affects Nexus 2000 Series Switches, Nexus 3000 Series Switches, Nexus 3500 Platform Switches, Nexus 3600 Platform Switches, Nexus 5500 Platform Switches, Nexus 5600 Platform Switches, Nexus 6000 Series Switches, Nexus 7000 Series Switches, Nexus 7700 Series Switches, Nexus 9000 Series Switches in standalone NX-OS mode, Nexus 9500 R-Series Line Cards and Fabric Modules, UCS 6100 Series Fabric Interconnects, UCS 6200 Series Fabric Interconnects, UCS 6300 Series Fabric Interconnects. Cisco Bug IDs: CSCuw99630, CSCvg71290, CSCvj67977.
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Analysis
by VulDB Data Team • 03/28/2023
The vulnerability described in CVE-2018-0291 represents a critical weakness in the Simple Network Management Protocol (SNMP) implementation within Cisco NX-OS software affecting multiple network infrastructure platforms. This issue stems from inadequate validation mechanisms within the SNMP input packet processor, specifically concerning the handling of SNMP protocol data units (PDUs) that form the core communication structure of SNMP operations. The flaw exists at the protocol parsing layer where the system fails to properly validate incoming SNMP packets before processing their contents, creating an exploitable condition that can be leveraged by authenticated remote attackers.
The technical exploitation of this vulnerability occurs through the crafting of malicious SNMP packets that contain malformed PDUs designed to trigger unexpected behavior in the SNMP application. When the affected Cisco devices receive these specially crafted packets, the improper validation causes the SNMP service to crash and restart repeatedly. This restart behavior can escalate to a complete system-level restart due to the cascading failure effects within the device's operating system, ultimately resulting in a denial of service condition that disrupts network management operations and potentially impacts overall network availability. The vulnerability affects a broad range of Cisco networking equipment including various Nexus switch series and UCS fabric interconnects, making it particularly concerning for enterprise network environments where these devices serve critical infrastructure functions.
The operational impact of this vulnerability extends beyond simple service disruption as it can compromise network management capabilities that organizations rely upon for monitoring and maintaining their infrastructure. Network administrators typically depend on SNMP for device status monitoring, performance tracking, and configuration management, making this DoS condition particularly disruptive. The authenticated nature of the attack means that an attacker must first establish valid credentials to exploit the vulnerability, but this requirement does not significantly reduce the threat level given that SNMP credentials can often be obtained through other means or may be default credentials that remain unchanged. The repeated restarts can also cause logging and monitoring systems to become overwhelmed with error messages, potentially masking other security incidents and complicating incident response efforts.
Mitigation strategies for this vulnerability should focus on immediate patching of affected devices with the Cisco security updates released to address the SNMP validation flaw. Network segmentation and access control measures can help reduce the attack surface by limiting which systems can communicate with affected devices, while implementing SNMPv3 with strong authentication and encryption mechanisms provides additional protection layers. Monitoring for unusual SNMP traffic patterns and implementing intrusion detection systems can help identify exploitation attempts before they cause significant disruption. Organizations should also conduct comprehensive inventory assessments to identify all affected devices and prioritize remediation efforts based on the criticality of each device within their network infrastructure. The vulnerability aligns with CWE-129, which addresses improper validation of input data, and represents a specific instance of the broader category of protocol processing vulnerabilities that fall under ATT&CK technique T1203, which involves exploiting weaknesses in network protocols to achieve system compromise.