CVE-2026-20107: Cisco APIC Object Model CLI DoS Vulnerability

CVE-2026-20107 Overview

A vulnerability in the Object Model CLI component of Cisco Application Policy Infrastructure Controller (APIC) could allow an authenticated, local attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. To exploit this vulnerability, the attacker must have valid user credentials and any role that includes CLI access.

This vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by issuing crafted commands at the CLI prompt. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Critical Impact
Authenticated local attackers with CLI access can cause device reloads, disrupting network fabric management and potentially impacting data center operations dependent on the APIC controller.

Affected Products

Cisco Application Policy Infrastructure Controller (APIC)
Cisco APIC Object Model CLI component
Systems with CLI access enabled for authenticated users

Discovery Timeline

2026-02-25 - CVE-2026-20107 published to NVD
2026-02-25 - Last updated in NVD database

Technical Details for CVE-2026-20107

Vulnerability Analysis

This vulnerability exists in the Object Model CLI component of Cisco Application Policy Infrastructure Controller (APIC), a critical component in Cisco's Application Centric Infrastructure (ACI) architecture. The APIC serves as the centralized policy management and network automation engine for ACI deployments, making it a high-value target for attackers seeking to disrupt data center operations.

The root cause of this vulnerability is classified under CWE-1220 (Insufficient Granularity of Access Control), though the primary technical issue is insufficient input validation in CLI command processing. When an authenticated user with CLI access submits specially crafted commands, the system fails to properly validate and sanitize the input before processing, leading to an unhandled exception that triggers a device reload.

The attack requires local access and valid user credentials with any role that grants CLI access. While this limits the attack surface compared to unauthenticated remote vulnerabilities, insider threats or compromised accounts with minimal privileges could exploit this flaw to cause significant service disruption.

Root Cause

The vulnerability stems from insufficient input validation in the Object Model CLI component. The CLI parser does not adequately validate or sanitize command input before processing, allowing malformed or crafted commands to reach internal components that are not designed to handle unexpected input formats. This results in an unhandled error condition that triggers the device to reload as a defensive measure.

Attack Vector

The attack requires an authenticated local attacker with valid credentials and any role that includes CLI access to the APIC. The attacker would connect to the APIC CLI interface and issue specially crafted commands designed to exploit the input validation weakness. The local attack vector means the attacker either has direct physical or console access, or has established a remote CLI session through SSH or similar protocols after authenticating with valid credentials.

The vulnerability mechanism involves sending malformed input through the CLI that bypasses initial parsing but causes errors during deeper processing stages. Technical details regarding the specific crafted commands are available in the Cisco Security Advisory.

Detection Methods for CVE-2026-20107

Indicators of Compromise

Unexpected APIC device reloads without scheduled maintenance windows
Anomalous CLI session activity from users with limited administrative roles
Repeated authentication attempts followed by system crashes
Error logs indicating CLI parsing failures or unhandled exceptions prior to reloads

Detection Strategies

Monitor APIC system logs for unexpected reload events and correlate with CLI session activity
Implement user behavior analytics to detect unusual CLI command patterns from authenticated users
Configure SIEM alerts for APIC crash events combined with recent login activity
Review authentication logs for accounts accessing CLI shortly before system instability

Monitoring Recommendations

Enable detailed audit logging for all CLI commands executed on APIC controllers
Deploy network monitoring to track SSH sessions and console access to APIC devices
Configure automated alerts for device reload events outside of maintenance windows
Implement session recording for CLI access to aid forensic investigation

How to Mitigate CVE-2026-20107

Immediate Actions Required

Apply the security patch from Cisco as soon as available
Review and restrict CLI access permissions to only essential users and roles
Audit current user accounts with CLI access and remove unnecessary privileges
Implement additional monitoring for CLI activity on APIC controllers

Patch Information

Cisco has published a security advisory addressing this vulnerability. Administrators should consult the Cisco Security Advisory for specific patch information, affected software versions, and upgrade paths. It is recommended to upgrade to a fixed software release as soon as one becomes available.

Workarounds

Restrict CLI access to only essential administrative accounts with a legitimate need
Implement role-based access control (RBAC) to limit CLI capabilities for standard users
Consider network segmentation to limit which systems can establish CLI sessions to APIC
Deploy APIC controllers in a high-availability configuration to minimize impact from single device reloads

bash

# Example: Audit users with CLI access on APIC
# Review user roles and restrict CLI access where not required
# Consult Cisco documentation for specific RBAC configuration commands
# Enable enhanced logging for CLI sessions