CVE-2010-3074 in EncFS
Summary
by MITRE
SSL_Cipher.cpp in EncFS before 1.7.0 uses an improper combination of an AES cipher and a CBC cipher mode for encrypted filesystems, which allows local users to obtain sensitive information via a watermark attack.
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Analysis
by VulDB Data Team • 09/25/2021
The vulnerability described in CVE-2010-3074 represents a critical cryptographic flaw in the EncFS encrypted filesystem implementation that has significant implications for data confidentiality. This issue affects EncFS versions prior to 1.7.0 and stems from the improper combination of cryptographic algorithms in the SSL_Cipher.cpp file. The vulnerability specifically involves the use of AES cipher in CBC mode, which creates a dangerous cryptographic configuration that undermines the security assurances typically expected from encrypted storage systems.
The technical flaw manifests through the watermark attack vector, where local attackers can exploit the improper cipher combination to extract sensitive information from encrypted filesystems. This occurs because the implementation fails to properly handle the interaction between the AES encryption algorithm and the CBC (Cipher Block Chaining) mode, creating predictable patterns in the encrypted data that can be analyzed to infer information about the plaintext content. The watermark attack takes advantage of the deterministic nature of certain cryptographic operations within the flawed implementation, allowing attackers to identify specific data patterns and potentially reconstruct portions of the original data.
From an operational impact perspective, this vulnerability creates a severe risk for users who rely on EncFS for protecting sensitive information. Local users with access to the system can exploit this weakness to gain unauthorized insights into encrypted data without requiring external network access or complex attack vectors. The vulnerability essentially undermines the fundamental security promise of encrypted filesystems, as it allows attackers to perform information leakage attacks that do not require breaking the encryption algorithm itself but instead exploit implementation weaknesses. This makes the vulnerability particularly dangerous in multi-user environments where local access privileges might be compromised.
The cryptographic weakness described in CVE-2010-3074 aligns with CWE-327, which addresses the use of weak or broken cryptographic algorithms, and demonstrates how improper implementation of well-established cryptographic primitives can create exploitable security gaps. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and information gathering, as attackers can use the watermark attack to extract sensitive information from encrypted storage. The vulnerability also reflects broader concerns about cryptographic implementation security, as highlighted in various security standards that emphasize the importance of proper algorithm combination and mode selection in cryptographic implementations.
Mitigation strategies for this vulnerability require immediate upgrading to EncFS version 1.7.0 or later, where the cryptographic implementation has been corrected to properly handle the AES cipher and CBC mode combination. System administrators should also implement additional monitoring to detect unauthorized local access attempts and consider implementing additional layers of security such as proper access controls and user privilege management. The fix addresses the root cause by ensuring that the cryptographic operations properly handle the chaining mechanisms and prevent the creation of predictable patterns that enable watermark attacks. Organizations should also conduct thorough security assessments of their encrypted storage implementations to identify any other potential cryptographic weaknesses that might create similar vulnerabilities in their security infrastructure.