CVE-2012-2317 in php5
Summary
by MITRE
The Debian php_crypt_revamped.patch patch for PHP 5.3.x, as used in the php5 package before 5.3.3-7+squeeze4 in Debian GNU/Linux squeeze, the php5 package before 5.3.2-1ubuntu4.17 in Ubuntu 10.04 LTS, and the php5 package before 5.3.5-1ubuntu7.10 in Ubuntu 11.04, does not properly handle an empty salt string, which might allow remote attackers to bypass authentication by leveraging an application that relies on the PHP crypt function to choose a salt for password hashing.
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Analysis
by VulDB Data Team • 12/07/2021
The vulnerability described in CVE-2012-2317 represents a critical weakness in PHP's cryptographic hashing implementation that affects multiple Linux distributions including Debian and Ubuntu. This flaw specifically targets the php_crypt_revamped.patch patch that was introduced to address certain security concerns but inadvertently created a regression in salt handling behavior. The vulnerability manifests when applications relying on PHP's crypt function attempt to process password hashes with empty salt strings, creating a scenario where authentication mechanisms can be bypassed through predictable cryptographic behavior.
The technical root cause of this vulnerability lies in how PHP's crypt function processes empty salt values during password hashing operations. When an empty salt string is provided, the patched implementation fails to properly generate or validate the salt component that should be used for cryptographic hashing. This results in predictable hash outputs that can be exploited by attackers to bypass authentication mechanisms that depend on proper password verification. The flaw operates at the cryptographic level where the expected behavior of the crypt function is not maintained, allowing attackers to craft specific inputs that will produce hash values that match expected authentication outputs without knowing the actual passwords.
From an operational impact perspective, this vulnerability creates significant security risks for web applications that rely on PHP's built-in password hashing functions for user authentication. Attackers can exploit this weakness to perform credential stuffing attacks, bypass login mechanisms, or gain unauthorized access to user accounts across applications that depend on the vulnerable PHP implementations. The vulnerability is particularly dangerous because it can be leveraged without requiring any special privileges or complex attack vectors, making it a high-value target for malicious actors seeking to compromise authentication systems. The impact extends beyond simple credential theft to potentially allow full system compromise when combined with other vulnerabilities or attack vectors.
The vulnerability aligns with CWE-254 in the Common Weakness Enumeration which categorizes this as a "Security Feature Inadequacy" where cryptographic implementations fail to properly handle edge cases such as empty inputs. From an ATT&CK framework perspective, this vulnerability maps to T1110.003 which covers "Brute Force / Credential Stuffing" and T1566.001 which addresses "Phishing: Spearphishing Attachment". The patch resolution requires updating the affected PHP packages to versions that properly handle empty salt strings, ensuring that the crypt function generates appropriate salt values even when empty strings are provided as input. Organizations should implement immediate patching procedures and monitor for any applications that might be relying on vulnerable PHP versions to prevent exploitation attempts.
This vulnerability demonstrates the importance of thorough testing during security patch development and highlights the potential for well-intentioned security improvements to create new attack surfaces. The issue was resolved through proper implementation of salt generation logic that ensures cryptographic strength regardless of input conditions, requiring system administrators to update their PHP installations to patched versions that maintain proper cryptographic behavior for all input scenarios. The resolution process involves verifying that the updated packages correctly implement the crypt function with appropriate handling of edge cases while maintaining backward compatibility for legitimate use cases.