CVE-2017-5999 in sysPass
Summary
by MITRE
An issue was discovered in sysPass 2.x before 2.1, in which an algorithm was never sufficiently reviewed by cryptographers. The fact that inc/SP/Core/Crypt.class is using the MCRYPT_RIJNDAEL_256() function (the 256-bit block version of Rijndael, not AES) instead of MCRYPT_RIJNDAEL_128 (real AES) could help an attacker to create unknown havoc in the remote system.
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Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified in CVE-2017-5999 represents a critical cryptographic weakness within the sysPass password management system version 2.x prior to 2.1. This flaw stems from the improper implementation of encryption algorithms that significantly undermines the security posture of the affected system. The issue specifically resides in the inc/SP/Core/Crypt.class file where the system utilizes MCRYPT_RIJNDAEL_256() instead of the more secure MCRYPT_RIJNDAEL_128, which would implement the proper AES encryption standard. This misconfiguration creates a fundamental weakness that can be exploited by malicious actors to compromise the confidentiality and integrity of stored password data. The vulnerability falls under the category of cryptographic weakness as classified by CWE-327, which specifically addresses the use of weak or broken cryptographic algorithms that can be easily compromised by attackers.
The technical implementation flaw involves the use of Rijndael with a 256-bit block size rather than the standard 128-bit block size that constitutes true AES encryption. The MCRYPT_RIJNDAEL_256() function implements a variant of the Rijndael algorithm that differs significantly from the Advanced Encryption Standard adopted by the National Institute of Standards and Technology. This deviation from established cryptographic standards creates potential attack vectors that exploit known weaknesses in the 256-bit block implementation. The system's failure to properly review and validate the cryptographic implementation against industry standards demonstrates a critical gap in security engineering practices. This weakness can be categorized under ATT&CK technique T1552.001, which involves unsecured credentials, as compromised encryption directly affects the protection of sensitive password information stored within the system.
The operational impact of this vulnerability extends beyond simple data encryption concerns, as it creates opportunities for sophisticated attacks that can lead to complete system compromise. An attacker who successfully exploits this weakness could potentially decrypt password databases, gain unauthorized access to user accounts, and escalate privileges within the system. The vulnerability's severity is amplified by the fact that it affects the core cryptographic functions of the password management system, which are designed to protect sensitive authentication information. The lack of proper cryptographic review and validation means that the system may be vulnerable to various forms of cryptanalysis, including known-plaintext attacks and differential cryptanalysis that exploit the inherent weaknesses in the 256-bit block implementation. This vulnerability directly impacts the system's ability to provide adequate security controls as specified in security frameworks such as NIST SP 800-57, which emphasizes the importance of using well-vetted cryptographic algorithms.
The recommended mitigation strategy involves upgrading to sysPass version 2.1 or later, which addresses the cryptographic implementation flaw by properly implementing AES with 128-bit blocks. Organizations should also conduct thorough cryptographic reviews of their systems to identify similar implementations of weak encryption algorithms. Security administrators should implement additional monitoring and logging mechanisms to detect potential exploitation attempts. The remediation process should include re-encryption of all previously stored password data using the corrected cryptographic implementation to ensure that any compromised information cannot be exploited by attackers. This vulnerability underscores the critical importance of cryptographic algorithm validation and the necessity of following established security standards rather than implementing custom or non-standard cryptographic solutions. The incident highlights the need for comprehensive security testing and peer review of cryptographic implementations, particularly in systems handling sensitive authentication data.