CVE-2021-47701 in OpenBMCS
Summary
by MITRE • 12/09/2025
OpenBMCS 2.4 allows an attacker to escalate privileges from a read user to an admin user by manipulating permissions and exploiting a vulnerability in the update_user_permissions.php script. Attackers can submit a malicious HTTP POST request to PHP scripts in '/plugins/useradmin/' directory.
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Analysis
by VulDB Data Team • 12/17/2025
The vulnerability identified as CVE-2021-47701 affects OpenBMCS version 2.4 and represents a critical privilege escalation flaw that undermines the system's access control mechanisms. This vulnerability resides within the user administration functionality of the platform, specifically targeting the update_user_permissions.php script located in the /plugins/useradmin/ directory. The flaw enables unauthenticated or low-privileged attackers to manipulate user permissions and elevate their access level from read-only user status to full administrative privileges, creating a significant security risk for organizations relying on this open-source BMC management solution.
The technical implementation of this vulnerability stems from insufficient input validation and access control checks within the update_user_permissions.php script. When attackers submit malicious HTTP POST requests to this specific endpoint, the application fails to properly verify the authenticity and authorization of the requesting user. This weakness allows an attacker to manipulate permission parameters and effectively bypass the normal user privilege management workflow. The vulnerability operates at the application layer and can be exploited through standard web-based attack vectors, making it particularly dangerous as it requires minimal specialized tools or knowledge to execute successfully.
From an operational impact perspective, this privilege escalation vulnerability poses severe consequences for organizations utilizing OpenBMCS 2.4 for their baseboard management controller operations. Once exploited, attackers gain full administrative access to the BMC system, which provides them with complete control over the managed hardware, including the ability to modify system configurations, access sensitive data, and potentially compromise the entire infrastructure. The implications extend beyond simple access control violations as BMC systems often serve as critical points of entry for physical server management, making this vulnerability particularly attractive to threat actors seeking persistent access to enterprise environments. This flaw directly violates the principle of least privilege and can lead to unauthorized system modifications, data exfiltration, and potential lateral movement within network environments.
Security practitioners should implement immediate mitigations including disabling unnecessary user administration endpoints when not actively required, implementing strict input validation and output encoding for all user permission-related scripts, and deploying network segmentation to limit access to BMC management interfaces. The vulnerability aligns with CWE-285, which addresses improper authorization issues, and maps to ATT&CK technique T1078 for valid accounts and T1548 for privilege escalation. Organizations should also consider implementing web application firewalls to monitor and block suspicious POST requests targeting the affected script, while conducting thorough access control reviews to ensure proper user privilege management. Regular security updates and patches should be applied immediately upon availability, as this vulnerability represents a known weakness that can be exploited by both skilled attackers and automated scanning tools, making it a high-priority remediation item for all affected systems.