CVE-2026-20107 is a vulnerability identified in the Object Model CLI component of Cisco Application Policy Infrastructure Controller (APIC), specifically affecting versions 6.1(1f), 6.1(2f), 6.1(2g), 6.1(3f), and 6.1(3g). The root cause is insufficient input validation of commands entered via the CLI prompt. An authenticated attacker possessing valid credentials and any role that includes CLI access can exploit this flaw by issuing specially crafted commands. Successful exploitation triggers an unexpected device reload, causing a denial of service (DoS) condition that disrupts network policy management and automation functions reliant on APIC. The vulnerability does not impact confidentiality or integrity but severely affects availability. The attack vector is local, requiring low attack complexity and no user interaction, but it does require privileges to access the CLI. No public exploits or active exploitation have been reported to date. The vulnerability highlights the importance of strict input validation and access control granularity in network management platforms. Cisco has published the vulnerability with a CVSS 3.1 base score of 5.5, reflecting medium severity due to the limited scope of impact and required privileges.

The primary impact of CVE-2026-20107 is a denial of service condition caused by unexpected device reloads of Cisco APIC controllers. This can disrupt network policy enforcement, automation, and overall fabric management in data centers and enterprise networks relying on Cisco ACI (Application Centric Infrastructure). Organizations may experience temporary loss of network control, degraded performance, and operational downtime, potentially affecting business continuity. While the vulnerability does not expose sensitive data or allow unauthorized changes, the loss of availability in critical network infrastructure can have cascading effects on dependent applications and services. Attackers with valid credentials could intentionally disrupt network operations, leading to increased operational costs and potential reputational damage. The requirement for authenticated CLI access limits the attack surface to insiders or compromised accounts, but insider threats or credential theft scenarios increase risk. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially in environments with weak credential management or insufficient access controls.

To mitigate CVE-2026-20107, organizations should: 1) Apply Cisco-provided patches or updates as soon as they become available for the affected APIC versions. 2) Restrict CLI access strictly to trusted administrators and enforce the principle of least privilege, ensuring only necessary roles have CLI permissions. 3) Implement strong authentication mechanisms, including multi-factor authentication (MFA), to reduce the risk of credential compromise. 4) Monitor and audit CLI access logs for unusual or unauthorized command usage to detect potential exploitation attempts early. 5) Employ network segmentation and access controls to limit local access to APIC devices, reducing the likelihood of unauthorized local attacks. 6) Regularly review and update user roles and permissions to ensure granularity aligns with operational needs, minimizing exposure. 7) Conduct security awareness training for administrators to recognize and prevent misuse of credentials or access. 8) Consider deploying intrusion detection/prevention systems (IDS/IPS) that can alert on anomalous CLI command patterns. These measures collectively reduce the risk of exploitation and limit the impact if an attack occurs.