CVE-2014-3462 in EncFS
Summary
by MITRE
The ".encfs6.xml" configuration file in encfs before 1.7.5 allows remote attackers to access sensitive data by setting "blockMACBytes" to 0 and adding 8 to "blockMACRandBytes".
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Analysis
by VulDB Data Team • 12/17/2024
The vulnerability identified as CVE-2014-3462 affects the encfs encrypted filesystem implementation prior to version 1.7.5, representing a critical security flaw in how cryptographic parameters are handled within the system's configuration files. This vulnerability specifically targets the ".encfs6.xml" configuration file that stores essential encryption parameters for the encfs system, making it a prime target for attackers seeking to compromise encrypted data stores. The flaw stems from improper validation of cryptographic settings that govern how message authentication codes are generated and applied to encrypted blocks, creating a pathway for unauthorized data access through manipulation of core encryption parameters.
The technical implementation of this vulnerability involves manipulation of two critical parameters within the encfs configuration structure: "blockMACBytes" and "blockMACRandBytes". When an attacker sets "blockMACBytes" to zero and simultaneously increases "blockMACRandBytes" by eight, they effectively disable the cryptographic message authentication code protection mechanism that ensures data integrity and authenticity. This manipulation fundamentally weakens the encryption scheme by removing the cryptographic binding that prevents tampering with encrypted data blocks. The vulnerability operates at the cryptographic protocol level, specifically targeting the authentication mechanisms that should prevent attackers from accessing or modifying encrypted content without proper authorization, as defined by CWE-310.
The operational impact of this vulnerability extends beyond simple data exposure to encompass complete compromise of the encrypted filesystem's integrity guarantees. Attackers can exploit this flaw to access sensitive data stored within encfs volumes, potentially gaining access to confidential information that was intended to remain protected. The vulnerability creates a scenario where encrypted data becomes accessible without proper authentication, effectively nullifying the encryption protection that users rely upon. This represents a severe degradation in security posture, as it allows remote attackers to bypass the fundamental security assumptions that make encrypted filesystems useful for protecting sensitive information. The attack vector is particularly concerning because it requires only configuration file manipulation, making it accessible to attackers who may not possess direct access to the encrypted data but can influence the configuration parameters.
Mitigation strategies for this vulnerability center on immediate software updates to encfs version 1.7.5 or later, which contain patches addressing the improper parameter validation. System administrators should conduct comprehensive audits of existing encfs configurations to identify any instances where the vulnerable parameter combinations have been implemented. Additionally, organizations should implement strict access controls over configuration files and establish monitoring procedures to detect unauthorized modifications to encryption parameters. The vulnerability highlights the importance of proper cryptographic parameter validation and the need for robust input sanitization in security-critical systems, aligning with ATT&CK technique T1552.001 for credential access and T1071.004 for application layer protocol usage. Organizations should also consider implementing configuration management practices that enforce secure parameter settings and maintain audit trails of configuration changes to prevent exploitation of similar vulnerabilities in the future.