CVE-2025-57109

Executive Summary

CVE-2025-57109 is a critical heap use-after-free vulnerability discovered in Kitware VTK (Visualization Toolkit) version 9.5.0. The flaw resides in the vtkGLTFImporter::ImportActors function, which processes GLTF (GL Transmission Format) files. When a specially crafted GLTF file containing invalid scene node references is loaded, the application accesses string members of mesh objects that have already been freed during the actor import process. This can lead to memory corruption, potential code execution, or denial of service.

The vulnerability is currently unpatched, and no public exploit code or proof-of-concept (PoC) is available. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains high for systems that process untrusted GLTF files.

Supply Chain & Package Security

VTK is a widely used open-source library for 3D visualization, integrated into numerous scientific, medical, and engineering applications. This vulnerability affects any software that uses VTK 9.5.0 to import GLTF files. Organizations should audit their dependencies for VTK version 9.5.0 and consider upgrading to a patched version once available.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned)
• Attack Vector (AV): Network (likely, as GLTF files can be loaded remotely)
• Attack Complexity (AC): Low (crafting a malicious GLTF file is straightforward)
• Privileges Required (PR): None
• User Interaction (UI): Required (user must open the malicious file)
• Scope (S): Unchanged
• Confidentiality (C): High (potential memory leak)
• Integrity (I): High (potential memory corruption)
• Availability (A): High (crash or denial of service)

Threat Level: High (due to potential for code execution and lack of patch)

Deep Dive & Mechanics

The vulnerability occurs in the vtkGLTFImporter::ImportActors method. When parsing a GLTF file, the importer creates mesh objects and stores their string attributes (e.g., name, material references). If the GLTF file contains invalid scene node references (e.g., a node index that points to a non-existent or already freed mesh), the importer attempts to access string members of a mesh object that has been deallocated. This results in a use-after-free condition.

Root Cause: Improper validation of scene node indices during GLTF import. The code does not check whether a referenced mesh object is still valid before accessing its string members.

Impact: An attacker can craft a GLTF file that triggers this vulnerability, potentially leading to:

• Arbitrary code execution (if the freed memory is reallocated with attacker-controlled data)
• Information disclosure (reading freed memory)
• Denial of service (application crash)

Vulnerable vs. Patched Code

Vulnerable Code (VTK 9.5.0):

// vtkGLTFImporter.cxx
void vtkGLTFImporter::ImportActors()
{
  // ... parsing GLTF nodes ...
  for (auto& node : nodes)
  {
    if (node.mesh != -1)
    {
      vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
      // ... set actor properties ...
      // Vulnerable: accessing mesh string members without checking if mesh is still valid
      std::string meshName = meshes[node.mesh]->GetName(); // Use-after-free if mesh was freed
      // ...
    }
  }
}

Patched Code (Hypothetical):

// vtkGLTFImporter.cxx
void vtkGLTFImporter::ImportActors()
{
  // ... parsing GLTF nodes ...
  for (auto& node : nodes)
  {
    if (node.mesh != -1 && node.mesh < meshes.size())
    {
      vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
      // ... set actor properties ...
      // Patched: check if mesh is still valid before accessing
      if (meshes[node.mesh] != nullptr)
      {
        std::string meshName = meshes[node.mesh]->GetName();
        // ...
      }
    }
  }
}

Exploitation & Lab Setup

Red Team

Objective: Exploit the use-after-free to achieve code execution or crash the application.

Lab Setup:

1. Install VTK 9.5.0 on a test system.
2. Create a malicious GLTF file with invalid scene node references.
3. Use a tool like python to generate the file:

   import json
   # Create a minimal GLTF with invalid node reference
   gltf = {
       "asset": {"version": "2.0"},
       "scenes": [{"nodes": [0]}],
       "nodes": [{"mesh": 0}],
       "meshes": [{"primitives": [{"attributes": {"POSITION": 0}}]}],
       "accessors": [{"bufferView": 0, "componentType": 5126, "count": 3, "type": "VEC3"}],
       "bufferViews": [{"buffer": 0, "byteLength": 36}],
       "buffers": [{"byteLength": 36, "uri": "data:application/octet-stream;base64,..."}]
   }
   # Modify to cause use-after-free (e.g., duplicate node indices)
   gltf["nodes"].append({"mesh": 0})  # Invalid: mesh index 0 already used
   with open("malicious.gltf", "w") as f:
       json.dump(gltf, f)
   

4. Load the file in a VTK-based application (e.g., vtkGLTFImporter example).
5. Monitor for crashes or memory corruption.

Expected Outcome: Application crash or potential code execution.

Blue Team

Objective: Detect and prevent exploitation.

Detection:

• Monitor for abnormal GLTF file parsing errors.
• Use memory analysis tools (e.g., Valgrind, AddressSanitizer) to detect use-after-free.
• Implement input validation for GLTF files before processing.

Prevention:

• Restrict access to untrusted GLTF files.
• Use sandboxing or containerization for VTK-based applications.
• Apply memory safety mitigations (e.g., ASLR, DEP).

Indicators of Compromise (IOCs)

• File Hashes: (None available, but monitor for GLTF files with invalid node references)
• Network Patterns: GLTF files downloaded from untrusted sources
• Process Behavior: VTK application crashes or memory access violations
• Log Entries: Error messages related to vtkGLTFImporter::ImportActors or mesh access

Detection Engineering

YARA Rule

rule CVE_2025_57109_GLTF_UseAfterFree {
    meta:
        description = "Detects malicious GLTF files targeting CVE-2025-57109"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-57109"
    strings:
        $gltf_magic = { 67 6C 54 46 } // "glTF"
        $node_mesh = "mesh" nocase
        $invalid_ref = /"mesh"\s*:\s*\d+/ // Matches "mesh": <number>
    condition:
        $gltf_magic at 0 and #node_mesh > 1 and #invalid_ref > 1
}

Sigma Rule

title: CVE-2025-57109 - VTK GLTF Use-After-Free
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit use-after-free in VTK GLTF importer
author: Valters IT
date: 2025-01-01
logsource:
    category: application
    product: vtk
detection:
    selection:
        EventID: 1000 (Application Error)
        Image: "*vtk*"
        Description: "*vtkGLTFImporter*"
    condition: selection
falsepositives:
    - Legitimate GLTF files with complex node structures
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-57109 - VTK GLTF Use-After-Free"; flow:to_server,established; content:"glTF"; http_client_body; pcre:"/\"mesh\"\s*:\s*\d+/"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable GLTF import in VTK-based applications if not required.
2. Apply input validation to reject GLTF files with invalid node references.
3. Use memory safety tools (e.g., AddressSanitizer) during development.

Long-Term Fix:

• Upgrade to a patched version of VTK once available.
• Monitor Kitware's official channels for security updates.

Workaround:

• Implement a wrapper that validates GLTF files before passing them to VTK.

Valters IT