CVE-2026-20200: Cisco IMC RCE Vulnerability

CVE-2026-20200 Overview

CVE-2026-20200 is an argument injection vulnerability [CWE-141] in the web-based management interface of Cisco Integrated Management Controller (IMC). An authenticated remote attacker with low privileges can execute arbitrary commands on the underlying operating system and elevate privileges to root. The flaw stems from improper validation of user-supplied input submitted through the web interface. Cisco disclosed the vulnerability in its security advisory cisco-sa-cimc-arg-inject-upSHdMfU.

Critical Impact
Low-privileged authenticated users can achieve root-level command execution on affected Cisco IMC systems, compromising the out-of-band management plane of Cisco UCS hardware.

Affected Products

Cisco Integrated Management Controller (IMC)
Cisco Unified Computing System (UCS) servers managed by IMC
Specific fixed release information is provided in the Cisco Security Advisory

Discovery Timeline

2026-08-05 - CVE-2026-20200 published to NVD
2026-08-06 - Last updated in NVD database

Technical Details for CVE-2026-20200

Vulnerability Analysis

Cisco IMC provides out-of-band management for Cisco UCS hardware, exposing a web-based interface for configuration and monitoring. The vulnerability resides in how the interface handles user-supplied input submitted through this management surface. Cisco categorizes the weakness as [CWE-141] Improper Neutralization of Parameter/Argument Delimiters, indicating that crafted input alters the argument structure of a downstream command.

An authenticated attacker with low-privilege credentials on the interface can inject crafted arguments that reach an underlying command execution path. Because the target command runs with root privileges on the appliance operating system, the injection results in privilege escalation from a low-privileged web account to full root shell access. This grants control over firmware, boot policies, virtual media, and any workloads managed by the affected controller.

Root Cause

The root cause is improper validation and neutralization of user-supplied input. The interface passes attacker-controlled values into commands executed on the underlying operating system without sanitizing argument delimiters. This permits argument injection that changes the meaning of the executed command.

Attack Vector

Exploitation requires network access to the IMC web interface and valid low-privileged credentials. The attacker submits crafted input to a vulnerable interface field or parameter. The affected component processes the input and passes it into a shell or program invocation running as root, executing commands chosen by the attacker. No user interaction is required beyond the attacker's own authenticated session.

No public exploit code or proof-of-concept has been observed for CVE-2026-20200 at the time of publication. Technical details are described in the Cisco Security Advisory.

Detection Methods for CVE-2026-20200

Indicators of Compromise

Unexpected root-owned processes spawned by the IMC web server process after HTTP requests to management endpoints
Web interface access logs containing shell metacharacters, argument delimiters (such as --, -o, $, backticks), or unusual URL-encoded payloads in form fields
New or modified accounts, SSH keys, or firmware configuration on the IMC appliance without a corresponding change ticket
Outbound network connections initiated from the IMC management interface to unfamiliar hosts

Detection Strategies

Monitor IMC audit logs and syslog exports for authentication events from low-privileged accounts followed by configuration or firmware changes
Alert on anomalous command execution patterns on the IMC operating system, particularly commands spawned by the web management daemon
Correlate IMC login events with subsequent lateral movement or credential access from the management network

Monitoring Recommendations

Forward IMC syslog and audit logs to a centralized SIEM or data lake for retention and correlation
Baseline normal administrative activity on the IMC interface and alert on deviations, such as off-hours access from unusual source IPs
Restrict and monitor network flows to the IMC management VLAN, treating any lateral connection attempts as high-priority alerts

How to Mitigate CVE-2026-20200

Immediate Actions Required

Apply the fixed Cisco IMC software release listed in the Cisco Security Advisory as soon as maintenance windows permit
Audit all IMC user accounts and remove unused, shared, or low-assurance credentials
Rotate credentials for any IMC account that could have been exposed, and enforce strong, unique passwords
Restrict access to the IMC management interface to a dedicated administrative network segment

Patch Information

Cisco has published fixed software versions in security advisory cisco-sa-cimc-arg-inject-upSHdMfU. Refer to the Cisco Security Advisory for the specific fixed release matrix for each affected UCS platform and IMC firmware train. Verify firmware versions after patching using the IMC CLI or the management interface version banner.

Workarounds

Isolate the IMC management interface on an out-of-band network reachable only from administrative jump hosts
Enforce role-based access control and grant only the minimum privileges required for each IMC user
Require multi-factor authentication for any account with access to the IMC management network
Disable or restrict the web-based management interface where CLI or Redfish access can meet operational needs

bash

# Example: restrict access to the IMC management VLAN with an upstream ACL
# Replace 10.10.10.0/24 with your admin jump-host subnet and
# 192.0.2.10 with the IMC management IP
access-list 150 permit tcp 10.10.10.0 0.0.0.255 host 192.0.2.10 eq 443
access-list 150 deny   tcp any host 192.0.2.10 eq 443 log
access-list 150 permit ip any any