CVE-2021-28186 in BMC
Summary
by MITRE • 04/06/2021
The specific function in ASUS BMC’s firmware Web management page (ActiveX configuration-2 acquisition) does not verify the string length entered by users, resulting in a Buffer overflow vulnerability. As obtaining the privileged permission, remote attackers use the leakage to abnormally terminate the Web service.
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Analysis
by VulDB Data Team • 04/10/2021
The vulnerability identified as CVE-2021-28186 resides within the ASUS Baseboard Management Controller (BMC) firmware implementation, specifically affecting the Web management page's ActiveX configuration-2 acquisition functionality. This represents a critical buffer overflow flaw that stems from inadequate input validation mechanisms within the firmware's web interface components. The vulnerability manifests when the system fails to properly validate string length parameters submitted by users through the web management interface, creating an exploitable condition that can be leveraged by remote attackers to execute malicious code.
The technical nature of this flaw aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The vulnerability specifically impacts the ActiveX component responsible for configuration management within the BMC firmware, which operates with elevated privileges due to the nature of BMC functionality. When an attacker submits maliciously crafted input exceeding the allocated buffer size, the system's memory management fails to contain the overflow, potentially allowing arbitrary code execution or service disruption. This vulnerability operates at the application layer and requires authentication to exploit, though the privilege escalation aspect suggests that authenticated access may be sufficient for exploitation.
The operational impact of CVE-2021-28186 extends beyond simple service disruption to potentially enable complete system compromise. As a BMC vulnerability, it affects the underlying management infrastructure that controls hardware-level functions including power management, system monitoring, and remote access capabilities. The ability to cause abnormal termination of web services represents a denial-of-service vector that can render the device inaccessible to legitimate administrators while potentially providing attackers with opportunities to escalate privileges. The vulnerability's classification as a buffer overflow aligns with ATT&CK technique T1210, which covers exploitation of remote services through buffer overflow attacks. This type of vulnerability can be particularly dangerous in enterprise environments where BMC systems are used for critical infrastructure management, as compromise of these systems can lead to complete network control.
Mitigation strategies for this vulnerability should focus on immediate firmware updates from ASUS to address the specific buffer overflow condition in the ActiveX configuration component. Network segmentation and access control measures should be implemented to restrict access to BMC management interfaces to authorized personnel only, reducing the attack surface. Additionally, monitoring for anomalous traffic patterns or repeated connection attempts to the BMC web interface can help detect exploitation attempts. The vulnerability demonstrates the importance of proper input validation and bounds checking in firmware implementations, particularly for components that operate with elevated privileges and provide direct access to system management functions. Organizations should also consider implementing network access controls to limit exposure of BMC interfaces to trusted networks only, as the vulnerability can be exploited remotely without requiring physical access to the device.