CVE-2021-28191 in BMC
Summary
by MITRE • 04/06/2021
The Firmware update function in ASUS BMC’s firmware Web management page 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-2021-28191 resides within the firmware update functionality of ASUS Baseboard Management Controllers BMCs, specifically within the web management interface. This flaw represents a critical security weakness that stems from inadequate input validation mechanisms within the firmware update process. The vulnerability manifests when the system fails to properly validate the length of user-supplied strings during firmware update operations, creating an exploitable buffer overflow condition that can be leveraged by remote attackers to compromise the affected system. The issue is particularly concerning because it affects the web management interface of BMCs, which are critical components responsible for out-of-band system management and remote administration functions.
The technical implementation of this vulnerability falls under CWE-121, which describes buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw occurs in the string handling logic of the web interface's firmware update module, where user input is directly processed without proper length validation. When an attacker supplies a maliciously crafted input string that exceeds the allocated buffer size, the excess data overflows into adjacent memory regions, potentially corrupting program execution flow and allowing arbitrary code execution. This buffer overflow vulnerability specifically impacts the web service handling firmware updates, making it possible for attackers to cause abnormal termination of the web management service and potentially gain deeper system access.
The operational impact of CVE-2021-28191 extends beyond simple service disruption to encompass potential privilege escalation and remote code execution capabilities. Attackers who can successfully exploit this vulnerability can leverage the buffer overflow to terminate the web service and potentially gain elevated privileges within the BMC environment. This represents a significant threat to system integrity since BMCs typically operate with high-level administrative privileges and provide access to critical system functions including power management, system monitoring, and firmware updates. The vulnerability's remote exploitability means that attackers do not require physical access to the system, making it particularly dangerous in networked environments where BMCs are exposed to external networks. According to ATT&CK framework, this vulnerability maps to T1059.007 for remote code execution and T1068 for local privilege escalation, with potential for lateral movement within the network infrastructure.
Mitigation strategies for this vulnerability should focus on immediate firmware updates from ASUS, as the company has likely released patches addressing the buffer overflow condition. Organizations should implement network segmentation to isolate BMC management interfaces from general network traffic, reducing the attack surface available to potential attackers. Additionally, monitoring for unusual web service termination patterns and implementing input validation controls can help detect exploitation attempts. The vulnerability also highlights the importance of secure coding practices in embedded systems and BMC implementations, particularly around input validation and memory management. Security teams should conduct comprehensive vulnerability assessments of all BMC systems within their environment to identify similar weaknesses and implement proper access controls to limit exposure to unauthorized users. The remediation process should include thorough testing of firmware updates in controlled environments before deployment to production systems to ensure that the patch does not introduce compatibility issues with existing management workflows.