CVE-2004-0263 in PHP
Summary
by MITRE
PHP 4.3.4 and earlier in Apache 1.x and 2.x (mod_php) can leak global variables between virtual hosts that are handled by the same Apache child process but have different settings, which could allow remote attackers to obtain sensitive information.
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Analysis
by VulDB Data Team • 07/13/2025
This vulnerability represents a critical information disclosure issue affecting PHP installations running within Apache web servers through the mod_php module. The flaw exists in PHP versions 4.3.4 and earlier, specifically impacting both Apache 1.x and 2.x server configurations where multiple virtual hosts share the same child process. The vulnerability stems from improper variable scoping mechanisms within PHP's execution environment, creating a scenario where global variables defined in one virtual host context can persist and be accessed by subsequent virtual hosts processed by the same Apache worker process. This cross-contamination of variables occurs due to insufficient cleanup of global variable states between different virtual host contexts, allowing sensitive data from one host to be inadvertently exposed to another.
The technical exploitation of this vulnerability leverages the shared memory space within Apache child processes where PHP maintains global variable state across requests. When multiple virtual hosts are configured with different security settings or configurations, the PHP runtime fails to properly reset or isolate global variables between these distinct host contexts. This creates a persistent state leak where variables containing sensitive information such as database credentials, session data, or application-specific configuration values can be accessed by unauthorized virtual hosts. The vulnerability operates at the intersection of process management and variable scoping, specifically targeting the mod_php module's handling of global variables within the Apache server architecture. According to CWE-200, this represents a weakness in information disclosure where sensitive data is unintentionally exposed due to improper variable isolation.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks. Remote attackers can exploit this flaw to gain access to sensitive information that might include database connection strings, API keys, or other confidential data stored in global variables. The vulnerability is particularly dangerous in shared hosting environments or multi-tenant configurations where multiple customers' virtual hosts share the same Apache child processes. Attackers can systematically test different virtual host configurations to identify which variables leak between contexts, potentially building a comprehensive profile of sensitive information accessible across the server. This vulnerability aligns with ATT&CK technique T1528, which describes the exploitation of information disclosure to access credentials and sensitive data, and represents a fundamental flaw in process isolation within web server environments.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to versions beyond 4.3.4 where the variable scoping issues have been addressed. Organizations should implement proper virtual host isolation through Apache configuration settings that prevent multiple virtual hosts from sharing the same child processes when sensitive data is involved. The recommended approach includes upgrading to PHP 4.3.5 or later versions, which contain fixes for the global variable leakage issue, and implementing proper process management configurations that ensure clean separation between virtual host contexts. Additionally, security-conscious administrators should review their Apache configurations to ensure that virtual hosts with different security requirements are not scheduled to run within the same child processes, thereby reducing the attack surface for this type of information disclosure vulnerability.