CVE-2019-1969 in NX-OS
Summary
by MITRE
A vulnerability in the implementation of the Simple Network Management Protocol (SNMP) Access Control List (ACL) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to perform SNMP polling of an affected device, even if it is configured to deny SNMP traffic. The vulnerability is due to an incorrect length check when the configured ACL name is the maximum length, which is 32 ASCII characters. An attacker could exploit this vulnerability by performing SNMP polling of an affected device. A successful exploit could allow the attacker to perform SNMP polling that should have been denied. The attacker has no control of the configuration of the SNMP ACL name.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/11/2023
The vulnerability identified as CVE-2019-1969 resides within the Simple Network Management Protocol access control list implementation of Cisco NX-OS Software, representing a critical security flaw that undermines network monitoring protocols. This issue affects network devices running Cisco NX-OS software where SNMP polling is configured to restrict access through access control lists. The vulnerability manifests when an attacker exploits an improper length validation mechanism within the SNMP ACL processing logic, specifically when dealing with maximum length ACL names. The flaw allows unauthorized remote access to network devices despite configured restrictions, creating a significant bypass mechanism for network monitoring protocols.
The technical root cause of this vulnerability stems from an inadequate validation check during the processing of SNMP ACL names when they reach the maximum permitted length of 32 ASCII characters. This improper length validation creates a condition where the system fails to correctly evaluate access control parameters, resulting in a logic flaw that permits unauthorized SNMP polling operations. The vulnerability is classified as a buffer over-read or length validation error, which aligns with CWE-129 Input Validation and CWE-682 Incorrect Calculation categories. The flaw exists in the software's ACL processing module where the system does not properly validate the boundary conditions of input parameters, specifically the ACL name length, leading to a bypass of intended access controls.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables attackers to perform comprehensive SNMP polling of network infrastructure without proper authentication. This capability allows adversaries to gather sensitive network information including device configurations, interface status, routing tables, and other critical operational data that should remain protected. The vulnerability affects network management systems that rely on SNMP for monitoring and management purposes, potentially exposing the entire network infrastructure to reconnaissance and further attacks. According to ATT&CK framework, this vulnerability maps to T1071.004 Application Layer Protocol: DNS and T1046 Network Service Scanning, as it enables unauthorized network reconnaissance through SNMP protocols. The attack vector is particularly concerning because it requires no authentication credentials and can be exploited remotely, making it a significant threat to network security posture.
Mitigation strategies for CVE-2019-1969 should prioritize immediate software patching from Cisco, as the vendor has released security updates addressing this specific vulnerability. Network administrators should also implement additional monitoring controls to detect unauthorized SNMP access attempts and configure network segmentation to limit SNMP access to trusted management systems. The implementation of network access control lists at multiple layers of the network infrastructure can provide additional defense in depth. Organizations should conduct thorough vulnerability assessments to identify all affected devices running Cisco NX-OS software and ensure proper configuration management practices are followed. The vulnerability demonstrates the importance of proper input validation and boundary condition checking in network security implementations, reinforcing the need for comprehensive security testing and code review processes. Additionally, implementing network monitoring solutions that can detect anomalous SNMP traffic patterns can help identify exploitation attempts before they result in successful reconnaissance activities.