CVE-2026-10789

Executive Summary

CVE-2026-10789 is a critical remote code execution vulnerability in Autodesk Fusion Desktop’s MCP (Model Communication Protocol) extension. The flaw is triggered when a user visits a maliciously crafted webpage while the MCP extension is enabled. Successful exploitation allows arbitrary code execution with the privileges of the current user, potentially leading to full system compromise. The vulnerability has a CVSS score of 9.6, indicating a severe risk. No patch is currently available, and no public proof-of-concept or exploit code has been released. The EPSS score is 0.0%, suggesting low exploitation activity at this time, but the high severity warrants immediate attention.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary Autodesk desktop application and its MCP extension, which is part of the Autodesk Fusion ecosystem.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
• Base Score: 9.6 (Critical)
• Attack Vector: Network (AV:N) – The attack is initiated via a malicious webpage.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: Required (UI:R) – The user must visit the malicious webpage.
• Scope: Changed (S:C) – The vulnerability can impact resources beyond the original scope.
• Confidentiality Impact: High (C:H) – Full data disclosure possible.
• Integrity Impact: High (I:H) – Complete data modification possible.
• Availability Impact: High (A:H) – Full denial of service possible.

Threat Level: Critical. The vulnerability allows arbitrary code execution with user privileges, and the attack vector is simple (webpage visit). No patch exists, making all affected systems vulnerable.

Deep Dive & Mechanics

The MCP extension in Autodesk Fusion Desktop is designed to enable communication between the desktop application and web-based content. The vulnerability stems from improper input validation or sanitization of data received from a webpage. When a user visits a malicious webpage, the MCP extension processes crafted data that triggers a code execution path. This could be due to a buffer overflow, use-after-free, or injection flaw in the extension’s handling of protocol messages.

Attack Flow:

1. An attacker hosts a malicious webpage containing specially crafted JavaScript or HTML.
2. The victim, with Autodesk Fusion Desktop running and MCP extension enabled, visits the page.
3. The webpage sends malicious data to the MCP extension via a local web server or inter-process communication.
4. The extension processes the data, leading to arbitrary code execution in the context of the current user.

Root Cause: Likely a lack of bounds checking or improper validation of input length or content in the MCP extension’s message handler.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, based on the vulnerability description, the vulnerable code likely involves a function that processes incoming MCP messages without proper validation. A patched version would include input sanitization, length checks, and safe memory handling.

Vulnerable Code (Hypothetical):

void handle_mcp_message(char *msg) {
    char buffer[256];
    strcpy(buffer, msg); // No bounds check
    // Process buffer
}

Patched Code (Hypothetical):

void handle_mcp_message(char *msg) {
    char buffer[256];
    strncpy(buffer, msg, sizeof(buffer) - 1); // Bounds check
    buffer[sizeof(buffer) - 1] = '\0';
    // Process buffer
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Autodesk Fusion Desktop with MCP extension enabled.
• Victim user must visit a malicious webpage.

Exploitation Steps:

1. Create a malicious HTML page that sends crafted data to the MCP extension.
2. Host the page on a web server (e.g., using Python’s http.server).
3. Lure the victim to visit the page (e.g., via phishing email).
4. The exploit triggers arbitrary code execution, allowing the attacker to run commands or deploy malware.

Example Malicious HTML (Conceptual):

<html>
<body>
<script>
// Crafted payload to exploit MCP extension
var payload = "A".repeat(1000); // Buffer overflow
// Send to MCP extension via localhost
fetch('http://localhost:8080/mcp', { method: 'POST', body: payload });
</script>
</body>
</html>

Note: No public exploit code is available. The above is a conceptual example.

Blue Team

Detection:

• Monitor for unusual network connections from Autodesk Fusion Desktop to localhost or external IPs.
• Look for processes spawned by Autodesk Fusion Desktop that are not typical (e.g., cmd.exe, powershell.exe).
• Use endpoint detection and response (EDR) to detect code injection or abnormal memory access.

Mitigation:

• Disable the MCP extension in Autodesk Fusion Desktop until a patch is available.
• Implement application whitelisting to prevent unauthorized executables.
• Educate users to avoid visiting untrusted websites while using Autodesk Fusion.

Indicators of Compromise (IOCs)

• Network: Connections from Autodesk Fusion Desktop to localhost on high ports (e.g., 8080, 9090).
• Process: Unusual child processes spawned by Fusion360.exe or AutodeskFusion.exe.
• File: Temporary files created in %TEMP% with suspicious names (e.g., exploit_*.tmp).
• Registry: Modifications to HKEY_CURRENT_USER\Software\Autodesk\Fusion related to MCP settings.

Detection Engineering

YARA Rule

rule CVE_2026_10789_MCP_Exploit {
    meta:
        description = "Detects potential MCP extension exploit payloads"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2026-10789"
    strings:
        $mcp_string = "MCP" nocase
        $payload = "A" * 256 // Example pattern
    condition:
        $mcp_string and #payload > 0
}

Sigma Rule

title: CVE-2026-10789 MCP Extension Exploit
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects suspicious network connections from Autodesk Fusion Desktop
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Image|endswith: 'Fusion360.exe'
        DestinationIp: '127.0.0.1'
        DestinationPort: 8080
    condition: selection
falsepositives:
    - Legitimate MCP communication
level: high

Suricata Rule

alert tcp $HOME_NET any -> $HOME_NET 8080 (msg:"CVE-2026-10789 MCP Extension Exploit"; flow:to_server; content:"MCP"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the MCP extension in Autodesk Fusion Desktop settings.
2. Block outbound connections from Autodesk Fusion Desktop to untrusted IPs.
3. Apply the principle of least privilege to user accounts.

Long-Term Fix:

• Await an official patch from Autodesk. Monitor Autodesk’s security advisories.
• Consider using application virtualization or sandboxing for Autodesk Fusion.

Workaround:

• Use a web proxy to filter malicious content.
• Educate users to avoid clicking on suspicious links while Autodesk Fusion is running.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert