CVE-2015-0721 in NX-OS
Summary
by MITRE
Cisco NX-OS 4.0 through 7.3 on Multilayer Director and Nexus 1000V, 2000, 3000, 3500, 4000, 5000, 5500, 5600, 6000, 7000, 7700, and 9000 devices allows remote authenticated users to bypass intended AAA restrictions and obtain privileged CLI access via crafted parameters in an SSH connection negotiation, aka Bug IDs CSCum35502, CSCuw78669, CSCuw79754, and CSCux88492.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/22/2022
This vulnerability represents a critical authentication bypass flaw in Cisco NX-OS software affecting multiple device families including the Nexus 1000V, 2000, 3000, 4000, 5000, 5500, 5600, 6000, 7000, 7700, and 9000 series switches. The issue stems from improper handling of SSH connection negotiation parameters that allows authenticated users to escalate their privileges without proper authorization checks. This vulnerability specifically impacts versions 4.0 through 7.3 of the NX-OS operating system, creating a persistent security gap across a wide range of enterprise networking equipment. The flaw enables attackers to bypass intended AAA (Authentication, Authorization, and Accounting) restrictions that are designed to control access to privileged command-line interfaces.
The technical implementation of this vulnerability occurs during the SSH connection negotiation process where crafted parameters can manipulate the authentication flow. When an authenticated user establishes an SSH session, the system fails to properly validate the session parameters, allowing malicious input to bypass the normal privilege escalation checks. This behavior creates a path where users who have already authenticated to the system can potentially gain elevated privileges without going through the proper authorization channels. The vulnerability is particularly concerning because it operates at the protocol level during connection establishment rather than through application-level flaws, making it more difficult to detect and mitigate.
The operational impact of this vulnerability is severe as it provides a direct path to privileged command-line access on critical network infrastructure. Attackers who can authenticate to the system can exploit this flaw to execute commands with administrative privileges, potentially leading to complete network compromise. This vulnerability affects network operations by creating an unauthorized access vector that could be used to modify configurations, view sensitive data, or disrupt network services. The wide range of affected device families means that organizations with diverse network infrastructures face significant exposure, as the vulnerability exists across multiple generations of Cisco switches. The presence of multiple bug IDs (CSCum35502, CSCuw78669, CSCuw79754, and CSCux88492) indicates the complexity and severity of the underlying issue.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates that address the SSH parameter handling flaw. Network segmentation and access controls should be reviewed to limit the potential impact of exploitation, while monitoring should be enhanced to detect unusual authentication patterns or privilege escalation attempts. The vulnerability aligns with CWE-284 (Improper Access Control) and represents a specific instance of privilege escalation through protocol manipulation. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and could be leveraged for lateral movement within networks. Organizations should also consider implementing additional security controls such as SSH key management, regular privilege reviews, and enhanced logging of CLI activities to detect potential exploitation attempts. The remediation process requires careful planning due to the critical nature of the affected network equipment and the potential for service disruption during patch application.