CVE-2026-20037 is a vulnerability in the Cisco Unified Computing System (UCS) Manager software, specifically related to the NX-OS CLI privilege levels. The flaw arises because read-only users are granted unnecessary privileges, allowing them to perform actions beyond their intended scope. An attacker who can authenticate locally as a read-only user can exploit this vulnerability by accessing the NX-OS CLI and subsequently creating or overwriting files on the system. This unauthorized file modification capability could lead to integrity violations, potentially enabling the attacker to alter system configurations or implant malicious files. The vulnerability affects a broad range of Cisco UCS Manager versions, spanning multiple releases from 4.0 through 4.3, indicating a long-standing issue across many deployments. The CVSS 3.1 base score is 4.4 (medium severity), reflecting that exploitation requires local access with low complexity and privileges but does not impact availability and has limited confidentiality and integrity impact. No public exploits have been reported yet, but the vulnerability could be leveraged in targeted attacks where an adversary has obtained read-only credentials. The root cause is improper privilege assignment in the NX-OS CLI, which should restrict read-only users from performing write or privileged operations. Cisco UCS Manager is widely used in enterprise data centers for managing server infrastructure, making this vulnerability relevant to organizations relying on Cisco UCS for critical operations.

The primary impact of CVE-2026-20037 is on the integrity of affected Cisco UCS Manager systems. An attacker with read-only credentials can modify or overwrite files, potentially altering system configurations or implanting malicious code. This could lead to unauthorized changes in the management plane of UCS infrastructure, undermining trust in system operations and potentially enabling further compromise or disruption. While availability is not directly affected, the integrity breach could cascade into operational issues or facilitate privilege escalation attacks. Organizations relying on Cisco UCS for data center management, cloud infrastructure, or critical enterprise services may face increased risk of insider threats or lateral movement by attackers who gain low-level access. The vulnerability's requirement for local authentication limits exposure to insiders or attackers who have already compromised user credentials, but the broad range of affected versions and widespread deployment increases the overall risk. The absence of known exploits in the wild reduces immediate threat but does not eliminate the potential for future targeted attacks. Failure to address this vulnerability could result in unauthorized configuration changes, data tampering, and erosion of security controls within critical infrastructure environments.

To mitigate CVE-2026-20037, organizations should first verify if their Cisco UCS Manager deployments run affected versions and prioritize upgrading to patched releases once Cisco issues updates. In the absence of patches, restrict access to the UCS Manager interface strictly to trusted administrators and implement strong authentication mechanisms such as multi-factor authentication to reduce the risk of credential compromise. Review and tighten role-based access controls to ensure that read-only users cannot access the NX-OS CLI or perform any privileged commands. Employ network segmentation and firewall rules to limit local access to UCS Manager systems, minimizing the attack surface for potential local attackers. Monitor logs and audit trails for unusual file modifications or unauthorized CLI activity indicative of exploitation attempts. Additionally, consider deploying host-based integrity monitoring solutions on UCS Manager servers to detect unauthorized file changes promptly. Regularly review and update user privileges to follow the principle of least privilege, ensuring no unnecessary elevated rights are granted to read-only roles. Finally, maintain an incident response plan that includes procedures for handling potential compromise of UCS infrastructure.