CVE-2008-3896 in Grub Legacy
Summary
by MITRE
Grub Legacy 0.97 and earlier stores pre-boot authentication passwords in the BIOS Keyboard buffer and does not clear this buffer before and after use, which allows local users to obtain sensitive information by reading the physical memory locations associated with this buffer.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/25/2025
The vulnerability identified as CVE-2008-3896 affects GRUB Legacy versions 0.97 and earlier, presenting a significant security risk during the pre-boot authentication process. This flaw resides in the fundamental design of how authentication credentials are handled before the operating system loads, creating a persistent exposure that extends beyond the typical runtime security boundaries. The issue specifically targets the BIOS keyboard buffer mechanism, which serves as a temporary storage area for input data during the system boot sequence. When users enter authentication passwords during the GRUB boot process, these credentials are stored in this buffer without proper sanitization, leaving sensitive information accessible to unauthorized parties who can inspect physical memory locations.
The technical implementation of this vulnerability stems from inadequate memory management practices within the GRUB Legacy bootloader. The bootloader fails to properly clear the BIOS keyboard buffer both before password entry and after authentication completion, creating a window of opportunity for information disclosure. This flaw operates at the system level rather than the application level, making it particularly dangerous because it occurs before the operating system has fully initialized and can implement standard security controls. The buffer remains accessible in physical memory, allowing attackers with sufficient privileges or access to memory inspection tools to retrieve stored passwords and other sensitive authentication data. This represents a classic case of improper data handling and memory sanitization, where sensitive information is not adequately protected during its lifecycle within the system's boot process.
The operational impact of CVE-2008-3896 extends beyond simple credential theft, as it compromises the foundational security of the entire boot process. Attackers can exploit this vulnerability to gain unauthorized access to systems protected by GRUB authentication, potentially leading to full system compromise. The vulnerability is particularly concerning because it affects systems during their most vulnerable state, when the boot process is underway and before standard security measures are active. This creates a scenario where even systems with strong operating system-level security can be compromised at the pre-boot stage, undermining the principle of layered security. The attack vector is relatively straightforward for local attackers who have physical access to the system or can execute code with sufficient privileges to inspect memory contents, making it a significant concern for environments where physical security cannot be guaranteed.
From a cybersecurity perspective, this vulnerability aligns with CWE-200 (Information Exposure) and CWE-312 (Sensitive Information Exposure), as it exposes authentication credentials through improper memory handling practices. The attack pattern corresponds to techniques described in the MITRE ATT&CK framework under T1547.001 (Registry Run Keys / Startup Folder) and T1068 (Local Port Forwarding) as it exploits system-level access points during boot operations. The remediation strategy involves upgrading to GRUB 1.98 or later versions where the bootloader properly clears the BIOS keyboard buffer and implements secure memory handling practices. Organizations should also implement physical security measures to prevent unauthorized access to systems during boot phases and consider additional boot-level security measures such as secure boot implementations. The vulnerability highlights the importance of proper memory sanitization practices throughout all system components, particularly those operating at the pre-boot level where traditional security controls are not yet active, and underscores the need for comprehensive security testing of boot processes and firmware components.