CVE-2025-0731: Unauthenticated File Upload RCE Vulnerability

CVE-2025-0731 Overview

CVE-2025-0731 is an unrestricted file upload vulnerability [CWE-434] disclosed in VDE Security Advisory #2025-012. An unauthenticated remote attacker can abuse a demo account to upload an .aspx file where a photovoltaic (PV) system picture is expected. The uploaded server-side script executes in the security context of the running web application user. The flaw requires no authentication or user interaction and is reachable over the network.

Critical Impact
Attackers can upload and execute arbitrary .aspx code on the affected web application, gaining code execution in the context of the hosting user account.

Affected Products

Product affected as described in VDE Security Advisory #2025-012
Web-based PV system management interface exposing a demo account
Specific vendor and version details: refer to the VDE advisory

Discovery Timeline

2025-02-26 - CVE-2025-0731 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-0731

Vulnerability Analysis

The application exposes an image upload endpoint intended for PV system pictures. The endpoint fails to validate file type, extension, and content before writing uploaded files to a web-accessible directory. Attackers can substitute an .aspx server-side script for the expected image. The IIS/ASP.NET handler subsequently parses and executes the file when it is requested. Because the upload path is reachable through a built-in demo account, no legitimate credentials are required to reach the vulnerable code path.

Execution occurs in the security context of the web application's runtime user. This grants the attacker access to any files, database connections, and network resources available to that identity. The confidentiality and availability impact rated in the advisory reflect limited data and service disruption within that context, while integrity impact stems from arbitrary write of executable content.

Root Cause

The root cause is missing server-side validation of uploaded files. The application relies on client-side or extension-based checks rather than verifying MIME type, magic bytes, and enforcing a strict allowlist of image extensions. Additionally, the upload directory permits script execution by the ASP.NET handler, converting a file write primitive into remote code execution.

Attack Vector

The attacker authenticates to the demo account, which is accessible without vendor-issued credentials. They then submit a crafted multipart upload containing an .aspx payload in place of a JPEG or PNG image. Once stored, the attacker requests the uploaded file by URL, causing the web server to execute the embedded C# or VB.NET code. See the VDE Security Advisory #2025-012 for vendor-provided technical details. No public exploit is listed on ExploitDB, and the CVE is not present on the CISA KEV catalog.

Detection Methods for CVE-2025-0731

Indicators of Compromise

Presence of .aspx, .ashx, or .asp files inside directories designated for user-uploaded PV system images.
Web server access logs showing POST requests to the picture upload endpoint originating from the demo account session.
Subsequent GET requests to newly created files in the image upload directory returning non-image content types.
Outbound network connections from the web application process to unfamiliar hosts following an upload event.

Detection Strategies

Alert on any file written to the PV picture upload directory whose extension is not in an image allowlist such as .jpg, .jpeg, .png, or .gif.
Inspect uploaded file magic bytes and flag content that does not match a valid image header.
Correlate authentication events for the demo account with file write and process execution events on the web server.

Monitoring Recommendations

Enable IIS request logging with full URI and User-Agent capture for the upload endpoint.
Monitor w3wp.exe child process creation for shells such as cmd.exe or powershell.exe.
Track file integrity on web root directories to detect unauthorized script deployment.

How to Mitigate CVE-2025-0731

Immediate Actions Required

Disable or remove the demo account until the vendor patch is applied.
Restrict network access to the management interface using firewall rules or VPN-only exposure.
Audit the picture upload directory for unauthorized .aspx files and remove any that are found.
Rotate credentials and inspect logs for signs of prior exploitation.

Patch Information

Refer to VDE Security Advisory #2025-012 for vendor-provided patched versions and update instructions. Apply the fixed release as soon as it is available in your environment.

Workarounds

Configure IIS to deny script execution in upload directories by removing handler mappings for .aspx and related extensions.
Enforce server-side file type validation using magic byte inspection in front of the vulnerable endpoint via a reverse proxy or WAF rule.
Block requests to the upload endpoint from unauthenticated sessions by disabling the demo account at the identity provider or application configuration level.

bash

# Example IIS web.config snippet to block script execution in upload folder
# Place this web.config inside the uploads directory
<configuration>
  <system.webServer>
    <handlers accessPolicy="Read">
    </handlers>
    <staticContent>
      <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="1.00:00:00" />
    </staticContent>
  </system.webServer>
</configuration>