After receiving the email from Progress titled "Action Required: Security Vulnerabilities for Telerik UI for ASP.NET AJAX" regarding a security vulnerability in the RadAsyncUpload control, I updated my nuget packages to the latest version:  2025.3.812.462 --> 2026.2.708.462.  Everything else in the update is working successfully except for any page in which the RadAsyncUpload control lives.  

When the page loads, I receive the following error:

Type : System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : Object reference not set to an instance of an object.
Source : Telerik.Web.UI
Help link : 
Data : System.Collections.ListDictionaryInternal
TargetSite : Void DescribeComponent(Telerik.Web.UI.IScriptDescriptor)
HResult : -2147467261
Stack Trace :    at Telerik.Web.UI.RadAsyncUpload.DescribeComponent(IScriptDescriptor descriptor)
   at Telerik.Web.UI.ScriptRegistrar.GetScriptDescriptors(Control control)
   at Telerik.Web.UI.RadWebControl.GetScriptDescriptors()
   at System.Web.UI.ScriptControlManager.RegisterScriptDescriptors(IScriptControl scriptControl)
   at Telerik.Web.UI.RadWebControl.RegisterScriptDescriptors()
   at Telerik.Web.UI.RadWebControl.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.HtmlControls.HtmlTableRow.RenderChildren(HtmlTextWriter writer)
   at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.HtmlControls.HtmlTable.RenderChildren(HtmlTextWriter writer)
   at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer)
   at System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.Page.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at Telerik.Web.UI.RadAjaxControl.RenderPageInAjaxMode(HtmlTextWriter writer, Control page)
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.Page.Render(HtmlTextWriter writer)
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Another application updated to the latest version using the RadAsyncUpload works perfectly fine.  After researching, I discovered that my "broken" application is session-less, and my other application (which updated successfully) had no issues whatsoever.  In the previous version, 2025.3.812.462, RadAsyncUpload worked perfectly with a session-less application.  I've since had to implement session in order to resolve both the page load issue and the security vulnerability for the RadAsyncUpload.

Hi,

I have to process the files in the UploadedFiles collection in a certain order (alphabetical). Is that possible from the collection (LINQ?) or should I save the files first to the TargetDirectory and go from there?

Marc

Facing the exception Could not find file 'C:\inetpub\wwwroot\source\App_Data\RadUploadTemp\16378221455987_23.PNG.tmp'. while uploading a file from RadAsyncUpload Control on an aspx Page, at the line 5 while trying to read the InputStream.

The Code is like below on Codebehind file;

Protected Sub AsnycUpload1_FileUploaded(sender As Object, e As FileUploadedEventArgs) Handles AsnycUpload1.FileUploaded
Try
Dim file As UploadedFile = AsnycUpload1.UploadedFiles.Item(0)
Dim bytes(file.ContentLength - 1) As Byte
file.InputStream.Read(bytes, 0, bytes.Length)
file.InputStream.Dispose()
Catch ex As Exception
doh(ex)
End Try
End Sub

please help in resolving the issue!

Drag and drop on the AsyncUpload control from file explorer or MS outlook works fine when I'm using Microsoft Edge. No issues.

My application is running under IE Mode (IE11 compatability) and in this case, drag and drop only works when dragging from the file explorer. When trying to drag from IE, the file or email does not get uploaded.

Is there anything that can be changed to make this work?

Good afternoon,

I'm currently running Telerik UI for ASP.NET AJAX R3 2023.  I am using the RadAsyncUpload with a AsyncHandler.ashx to copy the file to a RadUploadTemp on a file share.

This has been working perfectly for ages but recently large file updates have been failing e.g. a 2.1 GB file failing at 61%.  I'm being told this is due to a TCP Zero Window issue.

I assumed the chunked upload mechanism mitigates the issues caused by TCP window size restrictions, which can cause slowdowns or failures when uploading very large files in a single request. I am setting the upload ChunkSize value to 4194304.

I have the following settings in web.config:

  <system.web>    
    <httpRuntime maxRequestLength="2097151" executionTimeout="18000"/>
  </system.web>

  <system.webServer>
    <security>
      <requestFiltering>
        <requestLimits maxAllowedContentLength="4294967295"/>
      </requestFiltering>
    </security>
  </system.webServer>

Have you got any ideas as to why it might be failing for larger files, or what I can do to the configuration to prevent the TCP Zero Window error by pausing data transmission until the receiver is ready to accept more data?

Kind regards,

Richard

I found an issue where I had a webpage that has an AsyncUpload control and a text field. If the user enters text that contains angle brackets with some text between the brackets, the AsyncUpload throws some type of error.

I was able to reproduce this problem in the Telerik demo:

https://demos.telerik.com/aspnet-ajax/controls/examples/integration/gridandradasyncupload/defaultcs.aspx?product=asyncupload

Steps:

1. Click "Add new record"

2. In the Image Name field type "test <test.com>"

3. Upload an image file

4. Click checkbox to add record

5. Error occurs.

I'm using server side validation for certain controls on an asp.net web form page, which also contains a RadAsyncUpload control. 

When a user clicks save, I check to make sure these certain controls contain a value.  If this fails, we stop the save process and display a message to the user.  

During this process, any files to be uploaded are lost.  I need to retain them.

In the load event following this post back, the RadAsyncUpload control still has the uploaded files, but after fully loading the page, they're gone.

I'm already using the Post back Triggers property and this save button just happens to be the post back trigger.

How can I capture these files and "re-load" them into the control?

I am working with multiple RadAsyncUpload controls, and for each RadAsyncUpload, I use a RadProgressBar to track the progress of the file uploads. However, I am encountering an issue when uploading multiple files to one of the RadAsyncUpload controls. In this case, all the RadProgressArea components display unexpectedly, as shown in the screenshot below.

Can anyone help by providing sample code or advice to handle this case?