CVE-2024-11234 is a vulnerability identified in PHP versions 8.1.*, 8.2.*, and 8.3.* prior to versions 8.1.31, 8.2.26, and 8.3.14 respectively. The issue stems from improper input validation (CWE-20) in the handling of streams when a proxy is configured with the "request_fulluri" option enabled. Specifically, the URI passed through the proxy is not properly sanitized, which can be exploited to perform HTTP request smuggling attacks. HTTP request smuggling involves manipulating the way HTTP requests are parsed by intermediary devices such as proxies, allowing an attacker to send crafted requests that bypass security controls or access internal resources. In this case, the attacker can leverage the proxy to send arbitrary HTTP requests originating from the server itself, potentially accessing resources that are normally restricted from external users. The vulnerability has a CVSS v3.1 base score of 4.8, indicating medium severity, with network attack vector, high attack complexity, no privileges required, and no user interaction needed. Although no known exploits are reported in the wild, the flaw presents a risk especially in environments where PHP applications use proxy streams with the vulnerable configurations. The vulnerability affects a wide range of PHP versions commonly used in web applications, making it relevant for many deployments worldwide. The lack of proper URI sanitization in proxy stream contexts is a critical oversight that can lead to unauthorized internal resource access and potential data exposure or manipulation.

For European organizations, the impact of CVE-2024-11234 can be significant depending on their PHP deployment and proxy usage. Many European enterprises and public sector entities utilize PHP-based web applications, often behind proxies for load balancing, caching, or security purposes. If these proxies are configured with the "request_fulluri" option and the affected PHP versions are in use, attackers could exploit this vulnerability to perform HTTP request smuggling. This could allow unauthorized access to internal services, sensitive data, or administrative interfaces not intended for external exposure. Critical sectors such as finance, healthcare, government, and telecommunications could face data breaches or service disruptions. Additionally, attackers might leverage this access to pivot further into internal networks. The medium severity score reflects the need for caution but also indicates that exploitation requires specific conditions (proxy with request_fulluri enabled and high attack complexity). Nonetheless, the potential for unauthorized internal resource access poses a tangible risk to confidentiality and integrity of data within European organizations.

1. Upgrade PHP to the fixed versions: 8.1.31 or later, 8.2.26 or later, and 8.3.14 or later as soon as they are released by the PHP Group. 2. Review and audit proxy configurations, specifically the use of the "request_fulluri" option in stream contexts, and disable it if not strictly necessary. 3. Implement strict input validation and sanitization on all incoming HTTP requests at the application and proxy levels to detect and block malformed or suspicious requests. 4. Employ web application firewalls (WAFs) with rules designed to detect HTTP request smuggling attempts. 5. Restrict proxy usage to trusted internal networks and limit exposure of proxy endpoints to external users. 6. Monitor network traffic and logs for unusual HTTP request patterns indicative of request smuggling. 7. Conduct penetration testing focusing on HTTP request smuggling vectors to identify potential exploitation paths. 8. Educate development and operations teams about the risks of proxy configurations and secure stream handling in PHP applications.