CVE-2026-19219 in Telerik UI for ASP.NET AJAX
Summary
by MITRE • 09/02/2026
In Progress® Telerik® UI for AJAX prior to v2026.3.812, insufficient integrity protection of dialog request parameters used by the RadEditor file browser may allow an attacker who has obtained certain application encryption key material to alter the folders the file browser reads from, writes to, and uploads into, potentially resulting in remote code execution.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in Progress Telerik UI for AJAX prior to version 2026.3.812 centers on a critical failure in data integrity verification within the RadEditor component's file browser functionality. This flaw specifically affects how dialog request parameters are processed, revealing that while these parameters may be encrypted or obfuscated during transmission, they lack sufficient cryptographic integrity protection such as Message Authentication Codes (MAC) or digital signatures. In secure web application architectures, it is standard practice to ensure not only confidentiality but also authenticity and integrity of sensitive inputs. The absence of robust integrity checks means that an attacker who has successfully obtained the necessary application encryption key material can decrypt these parameters, modify their contents without detection, re-encrypt them using the same keys, and submit the tampered requests back to the server. This scenario highlights a classic breakdown in the principle of defense-in-depth where reliance on confidentiality alone is insufficient when integrity controls are missing or weakly implemented.
From a technical perspective, this vulnerability allows for unauthorized manipulation of file system operations managed by the RadEditor component. The file browser relies on specific parameters to determine source directories for reading files and target directories for writing new content or uploading attachments. By altering these path-related parameters in the request payload, an attacker can redirect these operations away from intended safe directories into arbitrary locations within the server's file system that are accessible by the application process identity. This capability effectively bypasses directory traversal protections if they rely solely on input validation rather than cryptographic integrity verification of the operational directives sent to the backend logic. The ability to write files to unexpected locations is particularly dangerous because it expands the attack surface beyond simple data exfiltration or defacement into more severe outcomes involving server compromise.
The operational impact of this vulnerability is severe, primarily due to its potential for leading to Remote Code Execution (RCE). If an attacker can control where uploaded files are stored and ensure that those locations are within a directory served by the web application with script execution permissions, they can upload malicious scripts such as ASP.NET pages or other executable content. Once these files reside in an accessible location, the attacker can trigger their execution through standard HTTP requests, thereby gaining arbitrary code execution capabilities on the host server. This aligns directly with CWE-79, which covers Cross-Site Scripting and related injection flaws that lead to remote code execution via file upload mechanisms. Furthermore, this vulnerability maps to MITRE ATT&CK technique T1505.003, Server Component Web Shell: ASPX, as the attacker may deploy a web shell to maintain persistent access and further pivot within the network environment after initial compromise through the Telerik component flaw.
Mitigation strategies for this issue must address both immediate remediation and long-term architectural improvements. The primary and most effective mitigation is to upgrade the Progress Telerik UI for AJAX library to version 2026.3.812 or later, where the developers have presumably implemented proper integrity checks such as HMACs on sensitive dialog parameters. For organizations unable to immediately patch due to compatibility constraints, temporary mitigations should focus on strict server-side validation of all file path inputs regardless of their encrypted state. Implementing allow-lists for permitted directories and ensuring that upload destinations are strictly confined to non-executable storage areas can reduce the risk of RCE even if parameter tampering occurs. Additionally, organizations should review their key management practices; since this vulnerability requires access to encryption keys, securing these secrets using hardware security modules or dedicated vault solutions reduces the likelihood of an attacker obtaining the necessary material to exploit the integrity flaw in the first place. Regular audits of third-party component configurations and adherence to secure coding standards that mandate both confidentiality and integrity for sensitive inputs are essential steps in preventing similar vulnerabilities in future development cycles.