CVE-2008-3899 in TrueCrypt
Summary
by MITRE
TrueCrypt 5.0 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. NOTE: the researcher mentions a response from the vendor denying the vulnerability.
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Analysis
by VulDB Data Team • 10/08/2018
The vulnerability described in CVE-2008-3899 represents a critical security flaw in TrueCrypt 5.0 that exposes sensitive authentication data through improper memory handling during pre-boot authentication processes. This issue specifically targets the BIOS keyboard buffer mechanism that TrueCrypt utilizes to store password information before system boot, creating a persistent security risk that persists beyond the normal authentication flow. The vulnerability stems from the software's failure to properly sanitize memory locations after password entry, leaving credentials accessible to local attackers who can directly read physical memory regions associated with the keyboard buffer.
The technical implementation of this vulnerability involves the improper management of system-level memory structures that are typically reserved for temporary input data processing. When TrueCrypt 5.0 processes pre-boot authentication, it stores the password in the BIOS keyboard buffer as part of its authentication workflow, but fails to execute proper memory clearing procedures before and after this operation. This design flaw creates a persistent memory leak that allows unauthorized access to the stored password data through direct memory examination techniques. The vulnerability directly relates to CWE-254, which addresses security weaknesses in the storage and handling of sensitive information in memory, and more specifically to CWE-119 which deals with weaknesses in memory handling that can lead to information exposure.
From an operational perspective, this vulnerability significantly impacts system security by providing local attackers with direct access to authentication credentials that should remain protected during the pre-boot phase. The attack vector is particularly concerning because it operates at the system level where memory access is unrestricted for local users, making it difficult to detect and prevent through traditional network-based security measures. Attackers can leverage various memory dumping tools and techniques to extract the password data from the BIOS keyboard buffer, effectively bypassing the encryption protection mechanisms that TrueCrypt is designed to provide. This vulnerability undermines the fundamental security premise of pre-boot authentication systems, where the assumption is that sensitive data is protected until the authentication process is complete.
The implications of this vulnerability extend beyond simple credential theft to represent a complete breakdown in the security model of the encryption software. The fact that the vendor reportedly denied the vulnerability status suggests a potential disagreement over the severity classification, but the technical reality remains that the memory handling practices create a persistent exposure that could be exploited by sophisticated local attackers. This situation highlights the importance of proper memory management in security-critical applications and demonstrates how seemingly minor implementation details can have significant security consequences. Organizations using TrueCrypt 5.0 would be advised to implement additional access controls and monitoring to detect unauthorized memory access attempts, while also considering immediate migration to more secure encryption solutions that properly handle sensitive data in memory.
The vulnerability aligns with several ATT&CK tactics including privilege escalation and credential access, as local users can leverage this weakness to gain access to authentication credentials that would normally be protected. The memory-based nature of the attack also relates to techniques described in ATT&CK for memory dumping and information gathering, making it a particularly relevant case study for understanding how low-level system interactions can create security vulnerabilities. This issue serves as a reminder of the critical importance of proper memory sanitization practices in security software development, particularly for applications that handle sensitive authentication data and operate in privileged system contexts where the risk of exposure is highest.