CVE-2012-2143 in PHP
Summary
by MITRE • 01/25/2023
The crypt_des (aka DES-based crypt) function in FreeBSD before 9.0-RELEASE-p2, as used in PHP, PostgreSQL, and other products, does not process the complete cleartext password if this password contains a 0x80 character, which makes it easier for context-dependent attackers to obtain access via an authentication attempt with an initial substring of the intended password, as demonstrated by a Unicode password.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability described in CVE-2012-2143 represents a critical weakness in the DES-based cryptographic function implementation within FreeBSD systems and their downstream applications. This flaw affects FreeBSD versions prior to 9.0-RELEASE-p2 and has widespread implications across various software products including PHP and PostgreSQL that rely on the system's crypt_des function for password hashing and authentication. The vulnerability stems from improper handling of password strings containing the 0x80 character, which is a significant deviation from standard cryptographic practices and creates exploitable conditions for unauthorized access attempts.
The technical flaw manifests when the crypt_des function encounters a password containing a byte value of 0x80, which is interpreted as a null terminator in C-style string processing. This causes the function to truncate the password at the first occurrence of this character, effectively processing only a portion of the complete password. This behavior creates a fundamental security weakness because attackers can exploit this limitation by crafting authentication attempts using only the initial substring of a password, rather than the full password. The vulnerability is particularly concerning when dealing with Unicode passwords, where the 0x80 character frequently appears in multibyte character representations, making the attack vector more prevalent in modern applications.
The operational impact of this vulnerability extends beyond simple authentication bypasses, as it fundamentally weakens the cryptographic security of password verification systems. Attackers can leverage this weakness to perform credential guessing attacks with significantly reduced computational requirements, as they only need to guess the initial portion of passwords rather than the complete credential. This vulnerability directly maps to CWE-120, which addresses buffer overflow conditions, and more specifically to CWE-310, which deals with cryptographic issues related to weak encryption or hashing. The attack pattern aligns with ATT&CK technique T1110.003, which covers credential access through brute force methods, and T1110.002 for password spraying attacks, as the truncated password processing creates predictable attack vectors.
The security implications are particularly severe in environments where Unicode passwords are common, such as internationalized applications or systems supporting multilingual user bases. The vulnerability affects not just FreeBSD systems directly but also any applications that depend on the system's crypt_des implementation, creating a cascading security risk across multiple software layers. Organizations using affected versions of FreeBSD should implement immediate mitigations including upgrading to FreeBSD 9.0-RELEASE-p2 or later, and ensuring that all applications relying on the crypt_des function are updated to handle password strings properly. Additionally, administrators should consider implementing additional authentication controls such as account lockout mechanisms and multi-factor authentication to compensate for the weakened password security. The vulnerability highlights the importance of proper string handling in cryptographic functions and demonstrates how seemingly minor implementation flaws can create significant security weaknesses in authentication systems.