CVE-2017-11317

Telerik.Web.UI in Progress Telerik UI for ASP.NET AJAX before R1 2017 and in R2 releases before R2 2017 SP2 uses weak encryption for the RadAsyncUpload component, allowing unauthenticated remote attackers to forge upload parameters, upload arbitrary files to the web server, and ultimately execute arbitrary code. The flaw is triggered simply by sending crafted requests to the vulnerable upload handler over the network, with no authentication or user interaction required. Successful exploitation gives an attacker arbitrary file upload and remote code execution in the context of the ASP.NET application, which is typically hosted on IIS web servers. Any site or application built with Telerik UI for ASP.NET AJAX is affected, and the weakness is confirmed exploited in the wild: it was added to CISA's Known Exploited Vulnerabilities catalog on 2022-04-11, and related reporting describes multiple hacking groups — including IIS/ASP.NET-focused APT actors — breaching a U.S. federal agency through it.

What to do: Upgrade Telerik UI for ASP.NET AJAX to R1 2017 or R2 2017 SP2 (or later) per vendor instructions, and verify the deployed Telerik.Web.UI.dll version in each application's bin folder. Given active in-the-wild exploitation of IIS/ASP.NET applications, review affected web servers for unauthorized uploads and web shells and rotate ASP.NET machine keys used with RadAsyncUpload.