CVE-2016-4793 in CakePHP
Summary
by MITRE
The clientIp function in CakePHP 3.2.4 and earlier allows remote attackers to spoof their IP via the CLIENT-IP HTTP header.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability described in CVE-2016-4793 represents a critical security flaw in the CakePHP web application framework affecting versions 3.2.4 and earlier. This issue stems from the improper handling of client IP address determination within the framework's core functionality, specifically in the clientIp function that is responsible for identifying the originating IP address of HTTP requests. The flaw enables malicious actors to manipulate the perceived source of their requests by injecting falsified IP addresses through the CLIENT-IP HTTP header, effectively bypassing security controls that rely on IP-based authentication or access restrictions.
The technical implementation of this vulnerability occurs because the CakePHP framework's clientIp function does not properly validate or sanitize the CLIENT-IP header value before using it to determine the client's IP address. This header, which is not part of the standard HTTP specification and is not automatically set by web servers, can be easily manipulated by attackers who control the request headers. When the framework processes this header without proper validation, it accepts the spoofed IP address as legitimate, allowing unauthorized access to systems or services that depend on IP-based security measures for their operation. This vulnerability directly relates to CWE-284, which addresses improper access control, and CWE-20, which covers improper input validation.
The operational impact of this vulnerability extends beyond simple IP address spoofing to potentially compromise entire application security models that rely on IP-based access controls. Attackers can exploit this weakness to bypass firewall rules, access restricted administrative interfaces, or circumvent rate limiting mechanisms that depend on IP addresses for enforcement. In environments where CakePHP applications are used for user authentication, session management, or access control, this vulnerability could allow unauthorized users to gain elevated privileges or access sensitive data. The implications are particularly severe in cloud environments or shared hosting scenarios where multiple applications might rely on IP-based security boundaries, as demonstrated by ATT&CK technique T1071.1004 for application layer protocol manipulation.
Mitigation strategies for this vulnerability require immediate attention from system administrators and security teams. The most effective solution involves upgrading to CakePHP version 3.2.5 or later, which contains the patched clientIp function that properly validates and sanitizes IP address information. Organizations should also implement additional security layers such as proper input validation at the web server level, monitoring for suspicious header patterns, and implementing robust access control mechanisms that do not rely solely on IP address verification. Network administrators should consider implementing header filtering rules at the reverse proxy or load balancer level to prevent unauthorized CLIENT-IP headers from reaching the application servers, thereby reducing the attack surface for this specific vulnerability.