CVE-2023-20115 in Nexus 3000
Summary
by MITRE • 08/23/2023
A vulnerability in the SFTP server implementation for Cisco Nexus 3000 Series Switches and 9000 Series Switches in standalone NX-OS mode could allow an authenticated, remote attacker to download or overwrite files from the underlying operating system of an affected device.
This vulnerability is due to a logic error when verifying the user role when an SFTP connection is opened to an affected device. An attacker could exploit this vulnerability by connecting and authenticating via SFTP as a valid, non-administrator user. A successful exploit could allow the attacker to read or overwrite files from the underlying operating system with the privileges of the authenticated user.
There are workarounds that address this vulnerability.
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Analysis
by VulDB Data Team • 08/23/2023
The vulnerability identified as CVE-2023-20115 represents a critical authorization flaw within the Secure File Transfer Protocol implementation of Cisco Nexus 3000 and 9000 series switches operating in standalone NX-OS mode. This weakness stems from insufficient validation of user privileges during SFTP session establishment, creating a path for authenticated attackers to escalate their privileges beyond intended boundaries. The vulnerability specifically affects devices running in standalone mode where the NX-OS operating system manages the switch functionality without integration into a larger network management framework. The flaw manifests when the system fails to properly enforce role-based access controls during the SFTP authentication process, allowing non-administrative users to potentially access restricted system resources.
Technical exploitation of this vulnerability requires an attacker to establish a valid SFTP connection using legitimate credentials from a non-administrator account. The underlying logic error occurs during the session initialization phase where the system does not adequately verify whether the authenticated user possesses sufficient privileges to access certain file system locations. This misconfiguration creates a scenario where file operations that should be restricted to administrative users can be performed by regular users who have successfully authenticated through the SFTP interface. The vulnerability demonstrates a clear failure in privilege enforcement mechanisms and represents a classic case of inadequate access control validation within network infrastructure devices. According to CWE classification, this corresponds to CWE-285: Improper Authorization, which specifically addresses situations where the system fails to properly enforce access controls for protected resources.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it provides attackers with the capability to overwrite critical system files or download sensitive operational data from the underlying operating system. This could potentially lead to complete system compromise, service disruption, or data exfiltration from network infrastructure devices that are typically considered secure due to their role within enterprise networks. The vulnerability affects Cisco Nexus 3000 and 9000 series switches in standalone mode, which are commonly deployed in data center environments where these devices serve as core network infrastructure components. Attackers could leverage this vulnerability to modify system configurations, install malicious software, or gain persistent access to the network through compromised switch devices. The potential for lateral movement within the network increases significantly since switches often serve as critical connectivity points between different network segments, making this vulnerability particularly dangerous in enterprise environments.
Cisco has issued workarounds to address this vulnerability, which typically involve implementing additional access control measures or modifying the SFTP service configuration to restrict file system access. Organizations should immediately evaluate their current SFTP configurations and implement the recommended mitigations to prevent exploitation. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the T1068: Exploitation for Privilege Escalation tactic. Network administrators should conduct comprehensive vulnerability assessments of their Cisco Nexus deployments to identify affected devices and ensure proper patching or workaround implementation. Regular monitoring of SFTP access logs becomes critical for detecting potential exploitation attempts, as unauthorized file operations would likely generate suspicious activity patterns that could alert security teams to ongoing attacks. The vulnerability underscores the importance of proper access control implementation in network infrastructure devices and highlights the need for continuous security testing of critical network components.