CVE-2026-13188 in Telerik UI for ASP.NET AJAX
Summary
by MITRE • 07/22/2026
In Progress® Telerik® UI for AJAX prior to v2026.2.708, DialogHandler request parameters may be tampered with, potentially altering dialog server-side behavior and enabling chained exploitation.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/22/2026
The vulnerability in Progress Telerik UI for AJAX prior to version 2026.2.708 represents a critical security flaw that allows attackers to manipulate DialogHandler request parameters, potentially leading to unauthorized server-side behavior modification and enabling sophisticated chained exploitation techniques. This issue stems from insufficient input validation and parameter sanitization within the dialog handling mechanism, creating an attack surface where malicious actors can alter request parameters to influence how dialogs are processed on the server.
The technical implementation flaw resides in the DialogHandler component's inadequate validation of incoming request parameters that control dialog behavior such as visibility, positioning, and execution flow. When developers integrate Telerik UI components into their web applications, the DialogHandler processes user-supplied parameters without proper sanitization or authorization checks, allowing attackers to inject modified values that can alter the intended server-side execution path. This vulnerability is particularly concerning because it operates at the request parameter level rather than requiring more complex exploitation techniques.
The operational impact of this vulnerability extends beyond simple parameter tampering, as it enables attackers to potentially escalate privileges and execute arbitrary code within the application context. By manipulating dialog parameters, adversaries can bypass security controls that rely on dialog state management, potentially gaining access to restricted functionality or data that should be protected. The chained exploitation capability means that an initial compromise through this vulnerability can serve as a foothold for more extensive attacks, including privilege escalation and data exfiltration.
This vulnerability aligns with CWE-20 "Improper Input Validation" and represents a specific instance of insecure parameter handling within web application frameworks. The ATT&CK framework categorizes this type of vulnerability under T1059 "Command and Scripting Interpreter" and potentially T1566 "Phishing" when used in conjunction with social engineering attacks that target the dialog interface components.
Organizations should immediately implement parameter validation controls that sanitize all incoming DialogHandler parameters, enforce strict access controls for dialog operations, and deploy web application firewalls to detect and block suspicious parameter modifications. Regular security assessments of Telerik UI components should include thorough testing of request parameter handling mechanisms, while developers should adopt secure coding practices that validate all user inputs before processing them within server-side components. The recommended mitigation strategy includes updating to the patched version 2026.2.708 or later, implementing comprehensive input validation at multiple layers, and establishing monitoring controls to detect anomalous dialog parameter usage patterns that may indicate exploitation attempts.