CVE-2021-21551 in DBUtil BIOS Driver
Summary
by MITRE • 05/04/2021
Dell dbutil_2_3.sys driver contains an insufficient access control vulnerability which may lead to escalation of privileges, denial of service, or information disclosure. Local authenticated user access is required.
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Analysis
by VulDB Data Team • 01/17/2025
The vulnerability identified as CVE-2021-21551 resides within the Dell dbutil_2_3.sys kernel driver, which is part of Dell's system management utilities. This driver operates at the kernel level and provides various system management functions including hardware configuration and monitoring capabilities. The flaw manifests as an insufficient access control mechanism that fails to properly validate user permissions when processing specific driver IOCTL (Input/Output Control) requests. According to the Common Weakness Enumeration framework, this vulnerability maps to CWE-284 which describes improper access control, specifically when a system fails to properly enforce access restrictions on sensitive operations or resources. The driver's lack of proper access validation creates a pathway for malicious code execution and privilege escalation.
The technical implementation of this vulnerability allows a local authenticated user to exploit the insufficient access control by sending specially crafted IOCTL commands to the vulnerable driver. These commands bypass normal permission checks and can manipulate system resources directly through kernel-level interfaces. The vulnerability's impact extends across multiple attack vectors including privilege escalation, where an attacker with standard user privileges could potentially gain administrative or kernel-level access to the system. Additionally, the flaw enables denial of service conditions through resource exhaustion or system instability caused by improper handling of malicious input. Information disclosure capabilities exist when the vulnerable driver exposes sensitive system information through improper response handling to specific IOCTL requests.
Operational exploitation of CVE-2021-21551 requires a local authenticated user account with the ability to interact with the vulnerable driver interface. This prerequisite aligns with the ATT&CK framework's privilege escalation techniques where adversaries leverage software vulnerabilities to gain elevated system privileges. The vulnerability affects Dell systems running specific versions of the dbutil_2_3.sys driver, typically those supporting enterprise and workstation configurations. The attack surface is particularly concerning in environments where local user access is not strictly controlled or where users may have access to system management utilities. The exploitation process typically involves identifying the vulnerable driver, crafting appropriate IOCTL requests, and executing the malicious payload to achieve the desired privilege escalation or system disruption.
Mitigation strategies for this vulnerability primarily focus on immediate patch management and system hardening measures. Dell has released security updates addressing this specific flaw in subsequent driver versions, making patch deployment the most critical remediation step for system administrators. The vulnerability's nature makes it particularly susceptible to exploitation in persistent attack scenarios where attackers maintain local access to target systems. Organizations should implement strict access controls and user permission management to limit local user privileges where possible. Additionally, monitoring systems should be configured to detect unusual IOCTL activity patterns that might indicate exploitation attempts. Security teams should also consider implementing kernel-mode exploit detection mechanisms and maintaining comprehensive system integrity monitoring to identify unauthorized driver modifications or access attempts against the vulnerable component. The vulnerability's classification under CWE-284 and its exploitation patterns align with common attack methodologies described in the MITRE ATT&CK framework for privilege escalation and defense evasion techniques.