CVE-2015-8867 in PHP
Summary
by MITRE
The openssl_random_pseudo_bytes function in ext/openssl/openssl.c in PHP before 5.4.44, 5.5.x before 5.5.28, and 5.6.x before 5.6.12 incorrectly relies on the deprecated RAND_pseudo_bytes function, which makes it easier for remote attackers to defeat cryptographic protection mechanisms via unspecified vectors.
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Analysis
by VulDB Data Team • 08/21/2022
The vulnerability CVE-2015-8867 represents a critical weakness in PHP's cryptographic implementation that affects multiple versions of the PHP interpreter. This issue specifically targets the openssl_random_pseudo_bytes function which is commonly used within web applications to generate cryptographically secure random numbers for various security purposes including session management, password generation, and cryptographic key creation. The vulnerability stems from PHP's reliance on the deprecated RAND_pseudo_bytes function from the OpenSSL library, creating a significant security gap that undermines the integrity of cryptographic operations.
The technical flaw manifests in how PHP's random number generation function handles the underlying OpenSSL library calls. When developers invoke openssl_random_pseudo_bytes, the function internally calls RAND_pseudo_bytes which has known weaknesses and predictable behavior patterns. This dependency creates a scenario where the random number generation becomes vulnerable to pattern recognition and prediction attacks, fundamentally compromising the security guarantees that applications expect from cryptographic random generation. The vulnerability is particularly concerning because it affects the core cryptographic functionality that many PHP applications depend upon for security operations.
The operational impact of this vulnerability extends far beyond simple random number generation issues. Attackers can exploit this weakness to predict or manipulate random values used in session tokens, password reset mechanisms, cryptographic keys, and other security-critical components. This makes it significantly easier for remote attackers to perform session hijacking, bypass authentication mechanisms, or compromise cryptographic protections that rely on unpredictable random values. The unspecified vectors mentioned in the CVE description indicate that attackers can leverage this weakness through various attack surfaces without requiring specific conditions or complex exploitation techniques.
This vulnerability aligns with CWE-330 Use of Insufficiently Random Values, which specifically addresses the use of weak random number generators in security-sensitive contexts. The issue also maps to ATT&CK technique T1083, which covers the discovery of system information through various reconnaissance activities, as attackers can potentially use predictable random values to gain insights into system operations. The weakness essentially creates a backdoor through which attackers can systematically undermine cryptographic protections that should provide strong security guarantees.
Organizations should prioritize immediate patching of affected PHP versions to address this vulnerability. The recommended remediation involves upgrading to PHP versions 5.4.44, 5.5.28, or 5.6.12 and later, which contain the necessary fixes to eliminate the dependency on the deprecated RAND_pseudo_bytes function. Additionally, security teams should conduct comprehensive audits of applications that rely on openssl_random_pseudo_bytes to identify potential attack surfaces and implement additional security controls. System administrators should also consider implementing monitoring for unusual patterns in random number generation that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date cryptographic libraries and avoiding deprecated functions that may contain known weaknesses.