Analysis Summary

The Cisco Integrated Management Controller (IMC) has been found to contain a critical privilege escalation vulnerability (CVE-2025-20261), which poses severe risks to enterprise environments, particularly those using Cisco UCS C-Series and S-Series servers. This flaw allows remote attackers to bypass authentication mechanisms and gain administrative access without valid credentials. The vulnerability stems from weaknesses in the IMC’s web interface authentication and authorization processes, enabling attackers to exploit insufficient input validation and access control mechanisms.

Technically, the vulnerability impacts the RESTful API endpoints, especially the /redfish/v1/ path, by leveraging poorly enforced session validation. Through the manipulation of JSON Web Tokens (JWTs) and session hijacking tactics, malicious actors can escalate privileges and execute high-level commands. This improper enforcement of role-based access control (RBAC) allows unauthorized users to interact with sensitive system configurations, monitor resources, and control management functions remotely, without being properly authenticated.

Exploiting this flaw enables attackers to interact directly with the Baseboard Management Controller (BMC), giving them capabilities to change BIOS settings, use out-of-band management, and potentially deploy persistent firmware-level malware. Moreover, attackers can abuse the Intelligent Platform Management Interface (IPMI) to access virtual media services, monitor system health, and intercept sensitive data, effectively compromising the integrity of data center operations and enabling lateral movement within the network.

Given its critical CVSS score of high, organizations using Cisco IMC should act immediately. The primary mitigation strategy is to update to the latest firmware that patches the vulnerability. Administrators must also implement multi-factor authentication, enforce strict firewall rules, especially on ports 80, 443, and 623, and isolate management networks through segmentation. Disabling unnecessary services and conducting regular audits of admin accounts, along with vigilant monitoring for suspicious API activity via SIEM systems, are essential steps to protect against potential exploitation.

Impact

• Sensitive Data Theft
• Privilege Escalation
• Security Bypass
• Gain Access

Indicators of Compromise

CVE

• CVE-2025-20261

Affected Vendors

Remediation

• Refer to the Cisco Security Advisory for patch, upgrade, or suggested workaround information.
• Isolate the IMC management interfaces from production or user-accessible networks to reduce exposure.
• Enable MFA for all administrative access to the IMC web interface to prevent unauthorized logins.
• Configure strict firewall policies to limit access to: TCP port 80 (HTTP), TCP port 443 (HTTPS), and TCP port 623 (IPMI over LAN)
• Turn off any unused services on the IMC interface to reduce the attack surface.
• Regularly review and remove unnecessary or inactive administrative user accounts.
• Use a Security Information and Event Management (SIEM) system to: Detect unusual API requests to /api/ and /redfish/v1/ endpoints, and Alert on unauthorized access attempts to the IMC web interface.