CVE-2015-4644 in PHP
Summary
by MITRE
The php_pgsql_meta_data function in pgsql.c in the PostgreSQL (aka pgsql) extension in PHP before 5.4.42, 5.5.x before 5.5.26, and 5.6.x before 5.6.10 does not validate token extraction for table names, which might allow remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted name. NOTE: this vulnerability exists because of an incomplete fix for CVE-2015-1352.
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Analysis
by VulDB Data Team • 05/21/2022
The vulnerability described in CVE-2015-4644 represents a critical denial of service flaw within PHP's PostgreSQL extension that stems from inadequate input validation during metadata extraction processes. This issue affects multiple PHP version lines including 5.4.x before 5.4.42, 5.5.x before 5.5.26, and 5.6.x before 5.6.10, demonstrating the persistence of flawed validation logic across different PHP release branches. The vulnerability specifically targets the php_pgsql_meta_data function located in the pgsql.c source file, which handles PostgreSQL database metadata operations. This function fails to properly validate token extraction for table names, creating a pathway for malicious input to trigger system instability.
The technical implementation of this vulnerability involves a NULL pointer dereference condition that occurs when the PostgreSQL extension attempts to process crafted table names without proper validation. When remote attackers submit specially crafted database object names, the function processes these inputs without sufficient sanitization, leading to a scenario where memory access violations occur. The incomplete fix for the previously disclosed CVE-2015-1352 vulnerability appears to have introduced this regression, suggesting that security patches may not have been thoroughly tested against all possible input scenarios. This flaw operates at the application level within the PHP runtime environment, making it particularly dangerous as it can be exploited through standard database connection and query operations.
From an operational impact perspective, this vulnerability creates a significant risk of application instability and service disruption for systems running affected PHP versions. Remote attackers can leverage this flaw to cause application crashes and system downtime, effectively implementing a denial of service attack against web applications that utilize PostgreSQL database connections. The vulnerability's exploitability is relatively straightforward since it only requires sending malformed table names through database operations, making it accessible to attackers with minimal technical expertise. Organizations relying on PHP-based web applications with PostgreSQL integration face potential business disruption, as the attack can be executed without requiring authentication or elevated privileges.
The security implications extend beyond simple service disruption to encompass potential broader system compromise risks, as application crashes may expose underlying system vulnerabilities or create opportunities for additional attack vectors. This vulnerability aligns with CWE-476 which addresses NULL pointer dereference conditions, and its exploitation pattern corresponds to techniques described in ATT&CK framework under process injection and denial of service tactics. Organizations should prioritize immediate patching of affected systems to mitigate this risk, as the vulnerability exists in widely deployed PHP versions and represents a known attack pattern that security researchers have documented in various threat intelligence feeds. The remediation process requires updating to patched PHP versions that contain proper token validation mechanisms and thorough input sanitization for PostgreSQL metadata operations.