CVE-2008-3901 in Software suspend 2
Summary
by MITRE
Software suspend 2 2-2.2.1, when used with the Linux kernel 2.6.16, stores pre-boot authentication passwords in the BIOS Keyboard buffer and does not clear this buffer after use, which allows local users to obtain sensitive information by reading the physical memory locations associated with this buffer.
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Analysis
by VulDB Data Team • 11/30/2017
The vulnerability described in CVE-2008-3901 represents a critical security flaw in the software suspend 2 implementation within Linux kernel versions up to 2.6.16. This issue specifically affects systems utilizing the suspend-to-disk functionality, commonly known as hibernation, where the system state is saved to disk and power is removed. The flaw occurs during the pre-boot authentication process when passwords are temporarily stored in the BIOS keyboard buffer, a hardware-level memory region that serves as a temporary storage area for keystrokes before they are processed by the operating system. This particular implementation fails to properly clear the buffer contents after authentication is complete, leaving sensitive credential information accessible in memory.
The technical exploitation of this vulnerability stems from the improper memory management practices within the suspend 2 subsystem. When a system enters hibernation mode and subsequently resumes, the pre-boot authentication mechanism stores user credentials in the BIOS keyboard buffer as part of the authentication sequence. The flaw lies in the fact that this buffer is not properly sanitized or cleared after the authentication process completes, allowing local attackers with physical access to the system to potentially read the raw memory contents where these passwords are stored. This creates a significant risk for systems where the BIOS keyboard buffer contents remain accessible in physical memory, as the stored credentials can be extracted through direct memory access techniques or by examining memory dumps.
The operational impact of this vulnerability extends beyond simple credential theft, as it fundamentally undermines the security assumptions of pre-boot authentication mechanisms. Attackers with local access can exploit this flaw to recover passwords that were entered during the hibernation resume process, potentially gaining access to encrypted volumes, network authentication systems, or other protected resources. The vulnerability is particularly concerning in environments where physical security is compromised or where systems are left in hibernation mode without proper security measures. According to CWE standards, this represents a weakness in memory management and credential handling, specifically categorized as CWE-254, which addresses security weaknesses in memory handling that can lead to information disclosure vulnerabilities.
The mitigation strategies for this vulnerability require both kernel-level patches and system administration practices. The primary fix involves updating the Linux kernel to versions that properly implement buffer clearing mechanisms during the suspend 2 process, ensuring that authentication credentials are securely erased from the BIOS keyboard buffer after use. System administrators should also implement physical security measures to prevent unauthorized access to systems during hibernation states, as well as consider disabling hibernation functionality on systems where the risk of physical access cannot be adequately controlled. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and privilege escalation through memory inspection, highlighting the importance of proper memory sanitization practices in system security design. Organizations should also consider implementing additional monitoring for suspicious memory access patterns and ensure that security patches are applied promptly to prevent exploitation of this and similar vulnerabilities in the suspend/resume functionality of their systems.