CVE-2008-4107 in PHP
Summary
by MITRE
The (1) rand and (2) mt_rand functions in PHP 5.2.6 do not produce cryptographically strong random numbers, which allows attackers to leverage exposures in products that rely on these functions for security-relevant functionality, as demonstrated by the password-reset functionality in Joomla! 1.5.x and WordPress before 2.6.2, a different vulnerability than CVE-2008-2107, CVE-2008-2108, and CVE-2008-4102.
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Analysis
by VulDB Data Team • 08/02/2021
The vulnerability described in CVE-2008-4107 represents a critical weakness in PHP's random number generation capabilities that fundamentally undermines cryptographic security assumptions. The rand and mt_rand functions in PHP 5.2.6 fail to produce cryptographically secure random numbers, creating a significant attack surface for malicious actors who can predict or manipulate the output of these functions. This flaw directly violates the principles of cryptographic randomness required for security-sensitive operations such as password generation, session management, and token creation. The vulnerability specifically affects systems where these functions are used for security-relevant purposes, making it particularly dangerous in web applications that rely on predictable random number generation for their security mechanisms.
The technical flaw lies in the implementation of PHP's random number generators which use deterministic algorithms that are unsuitable for cryptographic applications. These functions generate pseudo-random numbers using simple mathematical formulas that, while adequate for general programming purposes, do not meet the requirements for cryptographic security. The lack of proper seeding mechanisms and the use of predictable algorithms make it possible for attackers to reverse-engineer the sequence of generated numbers, thereby compromising the security of systems that depend on them. This weakness is particularly severe because it affects fundamental security operations within popular content management systems and web applications.
The operational impact of this vulnerability extends beyond simple predictability issues to encompass complete compromise of security mechanisms in affected applications. When applications like Joomla! 1.5.x and WordPress before version 2.6.2 utilize these functions for password reset functionality, attackers can exploit the predictable random number generation to bypass security controls. This allows unauthorized users to predict reset tokens, session identifiers, or password generation sequences, effectively granting them access to user accounts and system resources. The vulnerability demonstrates how seemingly minor implementation flaws in core programming functions can have devastating consequences for application security. Attackers can leverage this weakness to perform session hijacking, account takeover, and other malicious activities that would otherwise be prevented by proper cryptographic random number generation.
The implications of this vulnerability align with CWE-330, which addresses the use of insufficiently random values in cryptographic contexts, and can be mapped to ATT&CK technique T1112 for the exploitation of weak random number generation. Organizations using affected PHP versions must implement immediate mitigations including upgrading to patched PHP versions, implementing alternative cryptographic random number generators, and reviewing all security-relevant code that relies on the vulnerable functions. The recommended approach involves replacing rand and mt_rand with cryptographically secure alternatives such as openssl_random_pseudo_bytes or the random_bytes function introduced in later PHP versions. Additionally, security audits should be conducted to identify and remediate all instances where predictable random number generation is used for security purposes, ensuring that applications maintain proper entropy levels for cryptographic operations.
This vulnerability serves as a critical reminder of the importance of proper cryptographic implementation in software development. The widespread use of affected applications meant that this flaw exposed millions of users to potential security breaches, highlighting the need for comprehensive security testing and the adoption of established cryptographic standards. Organizations should prioritize regular security assessments and maintain up-to-date software to prevent exploitation of similar weaknesses in their systems. The incident also underscores the necessity of following security best practices such as using established cryptographic libraries and avoiding the use of non-cryptographic random number generators for security-sensitive operations. Proper implementation of cryptographic requirements, including the use of appropriate random number generation methods, is essential for maintaining the integrity and security of modern web applications and systems.