CVE-2025-57106

Executive Summary

CVE-2025-57106 is a critical heap-based buffer overflow vulnerability discovered in Kitware's Visualization Toolkit (VTK) up to version 9.5.0. The flaw resides in the BufferDataExtractionWorker template function within the vtkGLTFDocumentLoader module. An attacker can trigger this vulnerability by providing a specially crafted GLTF (GL Transmission Format) file containing malicious accessor data. Successful exploitation could lead to arbitrary code execution, denial of service, or information disclosure. The vulnerability is classified as a heap buffer overflow (CWE-122) and has been assigned a CVSS score of 0.0 in the NVD, but based on the technical details, a more realistic score is 9.8 (Critical). No public proof-of-concept (PoC) code or patch is currently available.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 9.8 (Critical)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

Threat Level: Critical. The vulnerability requires no authentication or user interaction and can be exploited remotely via a malicious GLTF file. Given VTK's widespread use in scientific visualization, medical imaging, and 3D rendering applications, the potential impact is significant.

Deep Dive & Mechanics

The vulnerability exists in the BufferDataExtractionWorker template function within vtkGLTFDocumentLoader.cxx. This function is responsible for extracting and processing binary data from GLTF accessor objects. GLTF accessors define how to read data from buffers, including the component type, count, and byte offset.

The root cause is a lack of proper bounds checking when copying data from the GLTF buffer into a VTK data array. Specifically, when the accessor specifies a byteOffset and count that, when combined with the component size, exceed the actual buffer size, the function writes beyond the allocated heap memory. This is a classic heap buffer overflow.

The vulnerable code path is triggered when VTK parses a GLTF file. The vtkGLTFDocumentLoader reads the accessor's byteOffset, count, and componentType from the JSON structure. It then calculates the total size of the data to be extracted as count * componentSize. This value is used to allocate a buffer. However, the function does not verify that byteOffset + totalSize is within the bounds of the source buffer. An attacker can craft a GLTF file where the accessor's byteOffset is set to a value close to the buffer size, and the count is set to a large number, causing the function to read and write beyond the allocated memory.

Vulnerable vs. Patched Code

Vulnerable Code (VTK <= 9.5.0):

The vulnerable code is in vtkGLTFDocumentLoader.cxx within the BufferDataExtractionWorker function. The exact line numbers may vary, but the logic is similar to:

template <typename T>
void BufferDataExtractionWorker(vtkGLTFDocumentLoader* loader,
                                vtkDataArray* array,
                                const GLTFBufferView& bufferView,
                                const GLTFAccessor& accessor)
{
  // ... get buffer data ...
  unsigned char* buffer = loader->GetBuffer(bufferView.buffer);
  vtkIdType bufferSize = loader->GetBufferSize(bufferView.buffer);

  // VULNERABLE: No check that accessor.byteOffset + (accessor.count * sizeof(T)) <= bufferSize
  T* data = static_cast<T*>(array->GetVoidPointer(0));
  memcpy(data, buffer + accessor.byteOffset, accessor.count * sizeof(T));
}

Patched Code (Hypothetical):

A patched version would include a bounds check before the memcpy:

template <typename T>
void BufferDataExtractionWorker(vtkGLTFDocumentLoader* loader,
                                vtkDataArray* array,
                                const GLTFBufferView& bufferView,
                                const GLTFAccessor& accessor)
{
  unsigned char* buffer = loader->GetBuffer(bufferView.buffer);
  vtkIdType bufferSize = loader->GetBufferSize(bufferView.buffer);

  // PATCHED: Validate that the requested data fits within the buffer
  size_t requestedSize = accessor.count * sizeof(T);
  if (accessor.byteOffset + requestedSize > bufferSize)
  {
    vtkErrorMacro("Buffer overflow detected in GLTF accessor data extraction.");
    return;
  }

  T* data = static_cast<T*>(array->GetVoidPointer(0));
  memcpy(data, buffer + accessor.byteOffset, requestedSize);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A target system running an application that uses VTK <= 9.5.0 and processes GLTF files.
• Ability to deliver a malicious GLTF file to the target (e.g., via web upload, email attachment, or network share).

Exploitation Steps:

1. Craft a Malicious GLTF File: Create a GLTF file with a buffer view and accessor that specify a byteOffset and count that cause an overflow. For example:

   • Buffer size: 100 bytes
   • Accessor byteOffset: 90
   • Accessor count: 100
   • Component type: FLOAT (4 bytes)
   • This would attempt to read 400 bytes starting at offset 90, overflowing the 100-byte buffer by 390 bytes.

2. Deliver the File: Send the malicious GLTF file to the target application.

3. Trigger the Vulnerability: The application loads the GLTF file, triggering the BufferDataExtractionWorker function and causing the heap buffer overflow.

4. Achieve Code Execution: Overwrite critical heap metadata or function pointers to hijack execution flow. This typically requires heap spraying and careful manipulation of the overflow data.

Example Malicious GLTF Structure (JSON):

{
  "buffers": [
    {
      "uri": "data:application/octet-stream;base64,AAAA...",
      "byteLength": 100
    }
  ],
  "bufferViews": [
    {
      "buffer": 0,
      "byteOffset": 0,
      "byteLength": 100
    }
  ],
  "accessors": [
    {
      "bufferView": 0,
      "byteOffset": 90,
      "componentType": 5126,
      "count": 100,
      "type": "SCALAR"
    }
  ],
  "meshes": [
    {
      "primitives": [
        {
          "attributes": {
            "POSITION": 0
          }
        }
      ]
    }
  ],
  "nodes": [
    {
      "mesh": 0
    }
  ],
  "scene": 0,
  "scenes": [
    {
      "nodes": [0]
    }
  ]
}

Blue Team (Detection & Defense)

Detection:

• Monitor for applications that load GLTF files and crash with heap corruption errors.
• Use memory analysis tools (e.g., Valgrind, AddressSanitizer) to detect out-of-bounds writes.
• Deploy endpoint detection and response (EDR) solutions that can detect heap spray or unusual memory allocation patterns.

Defense:

• Immediate: Disable or restrict the processing of GLTF files from untrusted sources.
• Mitigation: Apply input validation to GLTF files before they are processed by VTK. Check that accessor byteOffset and count values are within the bounds of the referenced buffer.
• Long-term: Apply the official patch from Kitware when it becomes available. Upgrade to a patched version of VTK.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (Example - replace with actual hashes if available)
  • malicious.gltf: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network Indicators:
  • HTTP requests containing Content-Type: model/gltf+json or model/gltf-binary from suspicious sources.
  • Unusual outbound connections from applications that process GLTF files.
• Behavioral Indicators:
  • Application crashes with heap corruption errors (e.g., HEAP CORRUPTION DETECTED in Windows Event Log).
  • High memory usage or unusual memory allocation patterns.
  • Presence of shellcode or ROP chains in memory dumps.

Detection Engineering

YARA Rule

rule CVE_2025_57106_GLTF_Overflow {
    meta:
        description = "Detects malicious GLTF files attempting to exploit CVE-2025-57106"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-57106"
        hash = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"

    strings:
        $json_header = "application/json"
        $gltf_magic = { 67 6C 54 46 } // "glTF"
        $accessor_key = "\"accessors\""
        $byte_offset_key = "\"byteOffset\""
        $count_key = "\"count\""

    condition:
        $gltf_magic at 0 and
        $accessor_key and
        $byte_offset_key and
        $count_key and
        // Check for suspiciously large count or offset values
        for any of ($byte_offset_key, $count_key) : (
            uint32be(@) > 1000
        )
}

Sigma Rule

title: CVE-2025-57106 GLTF Heap Buffer Overflow Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2025-57106 via heap corruption events
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-57106
logsource:
    product: windows
    service: application
    category: application_error
detection:
    selection:
        EventID: 1000
        Provider_Name: "Application Error"
        Faulting_Module_Name: "vtk*"
        Exception_Code: "0xc0000374"  # Heap corruption
    condition: selection
falsepositives:
    - Legitimate application crashes due to other bugs
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-57106 GLTF Heap Buffer Overflow Attempt"; flow:to_server; content:"Content-Type|3a| model/gltf+json"; http_header; content:"byteOffset"; http_client_body; content:"count"; http_client_body; pcre:"/byteOffset[\s]*:[\s]*\d{4,}/"; pcre:"/count[\s]*:[\s]*\d{4,}/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the processing of GLTF files from untrusted sources. If possible, block the model/gltf+json and model/gltf-binary MIME types at the network perimeter.
2. Mitigation: Apply input validation to GLTF files before they are processed by VTK. Specifically, verify that for each accessor, byteOffset + (count * componentSize) <= bufferView.byteLength.
3. Patch: Monitor Kitware's official channels for a security patch. Upgrade to a patched version of VTK as soon as it becomes available.
4. Workaround: If patching is not immediately possible, consider using a different 3D file format (e.g., OBJ, PLY) that does not trigger this vulnerability.
5. Monitoring: Deploy the YARA, Sigma, and Suricata rules provided in this report to detect exploitation attempts.

Valters IT
DevSecOps & Cyber Threat Intelligence