CVE-2007-2727 in PHP
Summary
by MITRE
The mcrypt_create_iv function in ext/mcrypt/mcrypt.c in PHP before 4.4.7, 5.2.1, and possibly 5.0.x and other PHP 5 versions, calls php_rand_r with an uninitialized seed variable and therefore always generates the same initialization vector (IV), which might allow context-dependent attackers to decrypt certain data more easily because of the guessable encryption keys.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability described in CVE-2007-2727 represents a critical cryptographic weakness in PHP's mcrypt extension that fundamentally undermines the security of encrypted data operations. This issue affects multiple PHP versions including 4.4.6 and earlier, 5.2.0 and earlier, and potentially 5.0.x releases, making it a widespread concern across numerous PHP installations. The flaw resides in the mcrypt_create_iv function which is responsible for generating initialization vectors used in cryptographic operations, specifically within the ext/mcrypt/mcrypt.c source file where the function implementation resides.
The technical root cause of this vulnerability stems from improper initialization of the random number generation process within PHP's cryptographic functions. When mcrypt_create_iv is invoked, it calls php_rand_r with an uninitialized seed variable, creating a deterministic behavior pattern that produces identical initialization vectors every time the function is executed under similar conditions. This violates fundamental cryptographic principles that require unpredictable and unique initialization vectors for each encryption operation to maintain security guarantees. The vulnerability maps directly to CWE-330, which specifically addresses the use of insufficiently random values in cryptographic contexts, and aligns with ATT&CK technique T1552.004 for unsecured credentials storage and data protection.
The operational impact of this vulnerability is significant and context-dependent, as it enables attackers to more easily decrypt sensitive data when they can predict or reproduce the initialization vectors used in encryption operations. Since the same IV is generated repeatedly, adversaries can potentially correlate encrypted data streams and perform statistical analysis attacks against the encryption scheme. This weakness particularly affects applications that rely on PHP's mcrypt extension for secure data transmission, file encryption, or database encryption where predictable IVs can compromise the confidentiality of encrypted information. The vulnerability is especially dangerous in environments where the same encryption keys are reused across multiple encryption operations, as it creates patterns that can be exploited to recover plaintext data without direct access to the encryption keys.
Mitigation strategies for this vulnerability require immediate patching of affected PHP versions to the recommended secure releases including PHP 4.4.7, 5.2.1, and subsequent versions. Organizations should also consider implementing additional security measures such as ensuring proper random seed initialization, using alternative cryptographic libraries that do not exhibit similar weaknesses, and conducting comprehensive security audits of all PHP applications that utilize mcrypt functions. System administrators should monitor for any applications that may be using deprecated mcrypt functionality and migrate to modern cryptographic standards such as OpenSSL or other well-established encryption libraries. The vulnerability serves as a critical reminder of the importance of proper random number generation in cryptographic implementations and the necessity of following established security practices for cryptographic operations.