CVE-2026-13182 in Telerik UI for ASP.NET AJAX
Summary
by MITRE • 07/22/2026
In Progress® Telerik® UI for AJAX prior to v2026.2.708, RadAsyncUpload client-state processing can distinguish decrypt failures from invalid-JSON parse failures, creating an oracle that reveals protected metadata values to remote attackers.
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Analysis
by VulDB Data Team • 07/22/2026
The vulnerability exists in In Progress Telerik UI for AJAX versions prior to v2026.2.708 where the RadAsyncUpload control fails to properly handle client-state processing errors. This flaw creates a cryptographic oracle that allows remote attackers to distinguish between decryption failures and invalid JSON parse failures, thereby exposing protected metadata values through subtle error differentiations.
The technical implementation of this vulnerability stems from improper error handling within the client-state decryption mechanism. When the system attempts to process encrypted client state data, it provides different error responses for decryption failures versus malformed JSON parsing errors. This differential response behavior creates an oracle that adversaries can exploit to infer information about the encryption keys or metadata structure. The flaw manifests as a timing-based side-channel where attackers observe how the system reacts to corrupted or manipulated data inputs.
This vulnerability directly relates to CWE-209, which addresses information exposure through error message analysis, and CWE-310, covering cryptographic issues including improper error handling during decryption operations. The attack surface represents a significant risk for applications utilizing Telerik UI controls, particularly those handling sensitive user data or authentication tokens within the client-state mechanism. The operational impact extends beyond simple information disclosure to potentially enable further attacks such as credential harvesting or session manipulation.
The vulnerability enables attackers to perform cryptographic oracle attacks against the RadAsyncUpload component, allowing them to extract protected metadata values that should remain confidential. This exposure can compromise user sessions, authentication tokens, and other sensitive data elements stored within the client-side state management system. The attack requires minimal privileges and can be executed remotely without requiring authentication to the application itself.
Mitigation strategies include updating to Telerik UI for AJAX version v2026.2.708 or later where the error handling has been corrected to provide consistent responses regardless of whether decryption fails or JSON parsing encounters issues. Organizations should also implement proper input validation and sanitization measures, ensure all cryptographic operations use constant-time comparison functions, and consider disabling unnecessary client-state features when they are not required for application functionality. Additionally, network-level monitoring should be implemented to detect unusual patterns in error responses that might indicate exploitation attempts against this vulnerability.