CVE-2015-6856 in Pre-Boot Authentication Driver
Summary
by MITRE
Dell Pre-Boot Authentication Driver (PBADRV.sys) 1.0.1.5 allows local users to write to arbitrary physical memory locations and gain privileges via a 0x0022201c IOCTL call.
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Analysis
by VulDB Data Team • 06/18/2024
The vulnerability identified as CVE-2015-6856 affects the Dell Pre-Boot Authentication Driver component known as PBADRV.sys version 1.0.1.5 which is part of Dell's hardware security infrastructure. This driver operates within the Windows kernel space and is responsible for managing pre-boot authentication processes that occur before the operating system fully loads. The flaw resides in how the driver handles IOCTL (Input/Output Control) requests, specifically the 0x0022201c command which is designed to control certain aspects of the authentication process. This vulnerability represents a critical security issue because it allows local attackers to escalate their privileges and potentially gain unauthorized access to sensitive system resources.
The technical implementation of this vulnerability stems from insufficient input validation and privilege checking within the PBADRV.sys driver. When a local user submits a specially crafted IOCTL request with the code 0x0022201c, the driver fails to properly validate the parameters or enforce appropriate access controls. This allows the attacker to manipulate the driver's behavior to write data to arbitrary physical memory addresses. The flaw essentially creates a path for privilege escalation where a user with minimal system access can directly interact with physical memory locations, bypassing normal kernel protection mechanisms. This type of vulnerability is categorized under CWE-787: "Out-of-bounds Write" and falls within the broader category of kernel-mode privilege escalation flaws that can enable attackers to execute code with system-level privileges.
The operational impact of this vulnerability is significant as it provides local attackers with the ability to modify critical system memory locations, potentially allowing them to alter the boot process, inject malicious code, or manipulate authentication mechanisms. Attackers could leverage this privilege escalation to install rootkits, modify system files, or disable security features that protect against unauthorized access. The vulnerability is particularly concerning because it operates at the kernel level where standard user-mode protections are bypassed, making it extremely difficult to detect and prevent. This flaw directly aligns with ATT&CK technique T1068: "Local Privilege Escalation" and can be used as a foundation for more advanced attacks targeting system integrity and confidentiality.
Mitigation strategies for CVE-2015-6856 should focus on immediate patching of the affected Dell systems, as the vendor has released updates to address this specific vulnerability. Organizations should also implement strict access controls and monitoring for kernel-mode drivers, particularly those involved in authentication and boot processes. System administrators should conduct thorough vulnerability assessments to identify any other potentially vulnerable components and ensure that all Dell systems running pre-boot authentication features are updated. Additional protective measures include implementing driver signature enforcement, disabling unnecessary kernel drivers, and monitoring for suspicious IOCTL activity that might indicate exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date firmware and drivers in enterprise environments where hardware security features are critical to overall system protection.