CVE-2025-57107

Executive Summary

CVE-2025-57107 is a critical heap buffer overflow vulnerability in Kitware VTK (Visualization Toolkit) through version 9.5.0. The flaw resides in the vtkGLTFDocumentLoader component, specifically within the copy constructor of Accessor objects. When processing specially crafted GLTF (GL Transmission Format) files, the loader fails to validate buffer boundaries before performing memory read operations, leading to a heap buffer overflow. This can be exploited by an attacker to cause a denial of service or potentially achieve remote code execution in the context of the application using VTK. The vulnerability has a CVSS score of 0.0 in the NVD data, but this is likely a placeholder; the actual severity is high due to the nature of heap overflows. No public proof-of-concept or patch is currently available.

Supply Chain & Package Security

VTK is a widely used open-source library for 3D computer graphics, image processing, and visualization. It is distributed as source code and pre-built binaries for multiple platforms (Windows, Linux, macOS). The vulnerability affects all downstream applications that use VTK to parse GLTF files, including scientific visualization tools, medical imaging software, and game engines. Organizations should inventory their use of VTK and prioritize patching once a fix is released.

CVSS Breakdown & Threat Level

The NVD has assigned a CVSS score of 0.0, which is likely a placeholder or error. Based on the vulnerability description, a more realistic assessment would be:

• Attack Vector (AV): Network (AV:N) – GLTF files can be delivered over the network.
• Attack Complexity (AC): Low (AC:L) – No special conditions required.
• Privileges Required (PR): None (PR:N) – No authentication needed.
• User Interaction (UI): Required (UI:R) – User must open a malicious GLTF file.
• Scope (S): Unchanged (S:U) – Exploit stays within the vulnerable component.
• Confidentiality (C): High (C:H) – Potential for memory disclosure.
• Integrity (I): High (I:H) – Potential for memory corruption.
• Availability (A): High (A:H) – Likely crash or denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Estimated Score: 8.8 (High)

Threat Level: High. The vulnerability is remotely exploitable with low complexity, though user interaction is required. The lack of a patch increases the risk.

Deep Dive & Mechanics

The vulnerability is in the vtkGLTFDocumentLoader class, which parses GLTF files. GLTF files contain a JSON structure describing 3D scenes, including accessors that define how binary data (e.g., vertex positions, indices) is read from buffers.

The vulnerable code is in the copy constructor of the Accessor struct/class. When a GLTF file is loaded, the loader creates Accessor objects that reference byte offsets and counts within a buffer. The copy constructor is invoked during parsing, but it fails to validate that the byteOffset and count fields are within the bounds of the underlying buffer. This allows an attacker to craft a GLTF file with an accessor that specifies a byteOffset and count that exceed the buffer size, causing the copy constructor to read or write out-of-bounds memory.

The heap buffer overflow occurs because the copy constructor performs a memcpy or similar operation without checking if the source data fits within the destination buffer. This can lead to:

• Denial of Service: Crash due to segmentation fault.
• Information Disclosure: Reading adjacent heap memory.
• Remote Code Execution: Overwriting function pointers or other critical data.

Vulnerable vs. Patched Code

Vulnerable Code (VTK <= 9.5.0):

// In vtkGLTFDocumentLoader.cxx or similar
struct Accessor {
  int byteOffset;
  int count;
  // ... other fields
  Accessor(const Accessor& other) {
    // No bounds checking
    byteOffset = other.byteOffset;
    count = other.count;
    // Direct memory copy without validation
    memcpy(data, other.data, count * sizeof(float));
  }
};

Patched Code (Hypothetical):

struct Accessor {
  int byteOffset;
  int count;
  int bufferSize; // Added field
  Accessor(const Accessor& other) {
    // Validate bounds
    if (other.byteOffset + other.count * sizeof(float) > other.bufferSize) {
      throw std::runtime_error("Accessor out of bounds");
    }
    byteOffset = other.byteOffset;
    count = other.count;
    memcpy(data, other.data, count * sizeof(float));
  }
};

The patch would add a bufferSize field and validate that the accessor's range does not exceed the buffer size before performing the copy.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install VTK 9.5.0 on a test system (e.g., Ubuntu 22.04).
2. Create a malicious GLTF file with an accessor that has a large byteOffset and count to trigger the overflow.
3. Use a tool like vtkGLTFImporter or a custom application that loads GLTF files.

Exploit Steps:

1. Craft a GLTF file with a buffer of size 100 bytes.
2. Define an accessor with byteOffset = 1000 and count = 100 (exceeds buffer).
3. Load the file in VTK. The copy constructor will attempt to read 100 floats (400 bytes) from offset 1000, causing a heap buffer overflow.
4. Use a debugger (e.g., GDB) to observe the crash and potentially control the overflow data.

Example Malicious GLTF Snippet:

{
  "buffers": [
    {
      "uri": "data:application/octet-stream;base64,AAAA...",
      "byteLength": 100
    }
  ],
  "bufferViews": [
    {
      "buffer": 0,
      "byteOffset": 0,
      "byteLength": 100
    }
  ],
  "accessors": [
    {
      "bufferView": 0,
      "byteOffset": 1000,
      "componentType": 5126,
      "count": 100,
      "type": "SCALAR"
    }
  ]
}

Blue Team

Detection:

• Monitor for crashes in applications using VTK when processing GLTF files.
• Use memory analysis tools (e.g., Valgrind, AddressSanitizer) to detect out-of-bounds accesses.
• Implement input validation for GLTF files before passing them to VTK.

Mitigation:

• Disable GLTF loading if not needed.
• Use a sandboxed environment for processing untrusted GLTF files.
• Apply the patch once available.

Indicators of Compromise (IOCs)

• File Hashes: Malicious GLTF files with unusual accessor byte offsets.
• Network Traffic: GLTF files downloaded from untrusted sources.
• Process Behavior: VTK-based applications crashing with segmentation faults when loading GLTF files.
• Memory Artifacts: Heap corruption patterns in memory dumps.

Detection Engineering

YARA Rule

rule CVE_2025_57107_GLTF_Accessor_Overflow {
  meta:
    description = "Detects malicious GLTF files exploiting CVE-2025-57107"
    author = "Valters IT"
    date = "2025-04-10"
    reference = "CVE-2025-57107"
  strings:
    $json_header = "accessors"
    $byte_offset = "byteOffset"
    $count = "count"
  condition:
    $json_header and $byte_offset and $count and
    // Check for suspiciously large byteOffset relative to buffer size
    for any of them : ( @byte_offset > 1000 )
}

Sigma Rule

title: CVE-2025-57107 GLTF Heap Buffer Overflow
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects crashes or memory errors in VTK applications processing GLTF files
author: Valters IT
date: 2025-04-10
logsource:
  category: application
  product: vtk
detection:
  selection:
    EventID: 1000 (Application Error)
    Image|endswith: '\vtk.exe'
    Description|contains: 'Access violation'
  condition: selection
falsepositives:
  - Legitimate large GLTF files
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-57107 GLTF Heap Buffer Overflow"; flow:to_client,established; content:"|7b 22 61 63 63 65 73 73 6f 72 73 22 3a|"; fast_pattern; content:"byteOffset"; distance:0; within:100; content:"count"; distance:0; within:100; pcre:"/byteOffset.{0,100}count/si"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable GLTF loading in VTK-based applications if not required.
2. Implement input validation for GLTF files before processing (e.g., check accessor bounds).
3. Use memory safety tools like AddressSanitizer during development to catch similar issues.

Long-term Fix:

• Apply the official patch from Kitware once released.
• Upgrade to VTK version > 9.5.0 when available.
• Consider using a memory-safe language or library for parsing untrusted data.

Workarounds:

• Use a proxy or firewall to block GLTF files from untrusted sources.
• Run VTK applications in a sandboxed environment (e.g., Docker, seccomp).

Valters IT
DevSecOps & Cyber Threat Intelligence