CVE-2011-4447 in bitcoind
Summary
by MITRE
The "encrypt wallet" feature in wxBitcoin and bitcoind 0.4.x before 0.4.1, and 0.5.0rc, does not properly interact with the deletion functionality of BSDDB, which allows context-dependent attackers to obtain unencrypted private keys from Bitcoin wallet files by bypassing the BSDDB interface and reading entries that are marked for deletion.
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Analysis
by VulDB Data Team • 02/19/2019
The vulnerability described in CVE-2011-4447 represents a critical security flaw in the Bitcoin wallet implementation that affects wxBitcoin and bitcoind versions prior to 0.4.1 and 0.5.0rc. This issue stems from improper handling of database operations within the Berkeley Database (BSDDB) system that Bitcoin clients use to store wallet information. The fundamental problem occurs when the wallet encryption feature attempts to interact with BSDDB's deletion mechanisms, creating a scenario where sensitive data remains accessible even after encryption is applied. The vulnerability specifically targets the interaction between the encryption process and the underlying database's garbage collection behavior, exposing a critical gap in how the software manages data persistence and security.
The technical root cause of this vulnerability lies in the way BSDDB handles deleted records within its database management system. When Bitcoin wallet entries are marked for deletion, BSDDB does not immediately remove the data from disk storage but instead maintains references to these records until a cleanup operation occurs. The encryption feature in affected Bitcoin clients fails to properly account for this behavior, allowing attackers to bypass the standard BSDDB interface and directly access database files. This creates an exploitable condition where unencrypted private key data remains readable in the database even after the wallet has been encrypted, as the deletion markers do not prevent direct file access. The vulnerability operates under the CWE-254 category of security weaknesses related to improper handling of data in database systems, specifically addressing issues with database integrity and data protection mechanisms.
The operational impact of this vulnerability is severe and directly affects the security posture of Bitcoin users who rely on wallet encryption for protection. Attackers with access to the wallet files can extract unencrypted private keys by directly reading the database entries that are marked for deletion, effectively bypassing the encryption mechanism entirely. This vulnerability undermines the fundamental security assumption that encrypted wallets provide protection against unauthorized access to private keys. The context-dependent nature of the attack means that it requires specific conditions to be exploited, such as access to the wallet file system and knowledge of the database structure, but once achieved, it provides complete access to all private keys stored in the wallet. This weakness significantly increases the risk of financial loss for Bitcoin users who depend on wallet encryption for asset protection.
Mitigation strategies for this vulnerability involve immediate software updates to versions 0.4.1 and 0.5.0rc or later, which contain the necessary fixes for proper BSDDB interaction during encryption operations. Users should also implement additional security measures such as filesystem-level encryption, regular backup verification, and monitoring for unauthorized access to wallet files. The fix implemented in the patched versions addresses the core issue by ensuring that the encryption process properly handles database deletion markers and prevents direct access to unencrypted data through the BSDDB interface. Organizations and individuals should also consider implementing multi-factor authentication for wallet access, regular security audits of wallet files, and adherence to security best practices for cryptocurrency storage. This vulnerability highlights the importance of proper database management in security-critical applications and serves as a reminder of the need for comprehensive testing of security features in financial software systems. The ATT&CK framework categorizes this vulnerability under persistence and credential access tactics, emphasizing the need for robust database security measures in cryptocurrency implementations.