CVE-2026-59504 in Portal Generator addon to ERP
Summary
by MITRE • 08/13/2026
CWE-602: Client-Side Enforcement of Server-Side Security
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Analysis
by VulDB Data Team • 08/13/2026
Client-side enforcement of server-side security represents a critical architectural flaw where security controls that should be implemented on the server side are instead enforced on the client side, creating vulnerabilities that can be easily bypassed. This weakness occurs when applications rely on client-side validation, authentication, or authorization mechanisms to protect sensitive resources or functionality that should only be accessible through proper server-side controls. The vulnerability stems from the fundamental misunderstanding that client-side security measures can adequately protect server-side resources, leading to a false sense of security that leaves systems exposed to various attack vectors.
The technical implementation of this weakness typically manifests when developers place trust in client-side code to enforce security policies that should inherently be validated on the server. This includes scenarios where client-side JavaScript validates user inputs, checks authentication tokens, or determines access permissions before sending requests to backend services. Attackers can easily bypass these protections by manipulating browser console variables, intercepting network traffic, or directly calling backend APIs without going through the client interface. The flaw directly violates the principle of server-side validation as outlined in owasp top ten category a05 and represents a classic case of trusting client-side data without proper server-side verification.
The operational impact of CWE-602 vulnerabilities extends far beyond simple data validation issues, potentially enabling complete system compromise through various attack vectors. An attacker exploiting this weakness can bypass authentication mechanisms to access restricted resources, manipulate application logic through modified client-side parameters, or perform unauthorized operations that should be restricted by proper server-side authorization controls. This vulnerability commonly leads to privilege escalation, data leakage, and unauthorized system modifications, as demonstrated in numerous real-world breaches where attackers bypassed client-side security checks to gain administrative access. The impact is particularly severe when combined with other vulnerabilities like cross-site scripting or man-in-the-middle attacks that allow attackers to modify client-side code during transmission.
Mitigation strategies for CWE-602 must focus on implementing proper server-side validation and enforcement of all security controls while recognizing that client-side measures should only serve as user experience enhancements rather than security barriers. Organizations should implement comprehensive server-side validation that independently verifies all inputs, authentication tokens, and authorization requests regardless of client-side state or parameters. Security controls should be designed with the principle that client-side code can always be modified by attackers, making any reliance on client-side enforcement inherently insecure. Proper implementation involves establishing robust backend validation routines, implementing proper session management, and ensuring that all critical security decisions are made server-side. Defense in depth strategies should include input sanitization, access control enforcement, and regular security testing to identify instances where client-side code might be relied upon for server-side security functions.
This vulnerability aligns with multiple ATT&CK techniques including T1078 Valid Accounts for privilege escalation, T1566 Phishing for credentials, and T1213 Data from Information Repositories for unauthorized data access. The weakness frequently appears in web applications that implement client-side routing or state management without proper server-side validation, creating opportunities for attackers to manipulate application behavior through direct API calls or parameter manipulation. Organizations should follow security standards such as iso 27001 and nist cybersecurity framework guidelines that emphasize server-side validation and proper access control implementation. Regular security assessments and penetration testing should specifically target client-server boundary controls to identify instances where server-side security is being bypassed through client-side enforcement mechanisms, ensuring that all security decisions are made at the appropriate trust level within the application architecture.