CVE-2003-1307 in PHP
Summary
by MITRE
** DISPUTED ** The mod_php module for the Apache HTTP Server allows local users with write access to PHP scripts to send signals to the server s process group and use the server s file descriptors, as demonstrated by sending a STOP signal, then intercepting incoming connections on the server s TCP port. NOTE: the PHP developer has disputed this vulnerability, saying "The opened file descriptors are opened by Apache. It is the job of Apache to protect them ... Not a bug in PHP."
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Analysis
by VulDB Data Team • 07/14/2025
The vulnerability described in CVE-2003-1307 relates to a potential security issue within the mod_php module of the Apache HTTP Server that could allow local users with write access to PHP scripts to manipulate server processes through signal handling mechanisms. This issue specifically involves the interaction between PHP script execution and the underlying Apache server process management, creating a potential vector for privilege escalation and resource manipulation. The vulnerability exists within the Apache module architecture where PHP scripts can potentially influence the process group of the Apache server, which represents a fundamental architectural concern in web server security.
The technical flaw manifests when a local user with write permissions to PHP script files can leverage the mod_php module's signal handling capabilities to send signals to the Apache server's process group. This allows the attacker to send a STOP signal to the server process, effectively pausing the web server operations, and then subsequently intercept incoming connections on the server's TCP port. The vulnerability stems from insufficient process isolation between the PHP execution environment and the Apache server process, creating a scenario where PHP scripts can directly manipulate the server's process lifecycle through signal transmission mechanisms. This represents a classic case of inadequate privilege separation and process control within the web server architecture.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable more sophisticated attacks involving process manipulation and resource hijacking. When an attacker can send STOP signals to the Apache server, they effectively gain the ability to pause server operations and then resume them at will, potentially creating a window for connection interception and data manipulation. The ability to use the server's file descriptors represents a particularly dangerous aspect, as it allows attackers to potentially access or manipulate files that would normally be protected by Apache's security mechanisms. This vulnerability directly impacts the integrity and availability of web services, as it can be exploited to create denial of service conditions or to gain unauthorized access to server resources that should remain protected.
The security implications of CVE-2003-1307 align with several cybersecurity frameworks and threat modeling concepts, particularly those addressing privilege escalation and process control vulnerabilities. From a CWE perspective, this issue relates to CWE-276: Incorrect Permission Assignment, as it involves improper handling of process permissions and file descriptor access. The vulnerability also connects to ATT&CK techniques involving process injection and privilege escalation, where attackers manipulate process groups to gain elevated access to system resources. The disputed nature of this vulnerability by the PHP developer indicates that the security community has debated the proper responsibility boundaries between Apache and PHP modules, with the PHP team arguing that Apache should be responsible for protecting file descriptors rather than PHP handling them. This debate highlights the complexity of modern web server architectures where multiple modules interact and share system resources, creating potential security gaps when proper isolation mechanisms are not implemented.
Mitigation strategies for this vulnerability should focus on implementing proper process isolation and privilege separation between the Apache server and PHP execution environments. System administrators should ensure that PHP scripts are executed with minimal privileges and that appropriate access controls are implemented to prevent local users from manipulating server processes. The recommended approach involves configuring Apache with proper security modules and ensuring that file descriptor access is properly restricted. Additionally, regular security audits should verify that no unnecessary permissions are granted to PHP script execution contexts, and that the server configuration properly isolates different execution environments. The vulnerability serves as a reminder of the importance of maintaining clear security boundaries between different components in complex web server architectures, particularly when dealing with module-level interactions that can affect system-level processes and resources.