# CVE-2026-9535: VTK vtkChacoReader out-of-bounds read in InputGraph2

Source: https://junglewise.ai/threats/cve-2026-9535-a-out-of-bounds-read-vulnerability-exists-in-the-vtkchacoreader  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-9535 · Severity: high · CVSS 8.2 · Published 2026-10-29

VTK is an open-source 3D visualization and scientific computing library used by researchers and engineers. A flaw in the Chaco file parser fails to validate vertex IDs in graph files, allowing a malicious .graph file to trigger an out-of-bounds read that can crash the application or leak memory contents.

Technologies: [Kitware VTK](https://junglewise.ai/threats/technologies/kitware-vtk). Vendors: [Kitware](https://junglewise.ai/threats/vendors/kitware).

## Quick answers

**Is CVE-2026-9535 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-9535 being exploited in the wild.

**How severe is CVE-2026-9535?** High severity, with a CVSS score of 8.2, published 29 October 2026.

**Which products and versions are affected?** Kitware VTK 9.6.1.

**Is there a fix for CVE-2026-9535?** Yes: fixed in VTK 9.6.2, 9.7.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-9535 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-9535?** Check whether you run Kitware VTK at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in VTK 9.6.2, 9.7.1

## Technical details

An out-of-bounds read (CWE-125) exists in vtkChacoReader::InputGraph2(), which parses Chaco plain-text graph format files. The vulnerability occurs because neighbor vertex IDs read from the .graph file are never validated to fall within the valid range [1, nvtxs] before being stored in the connectivity array. When GetCell() later attempts to retrieve point coordinates using these unchecked IDs as indices, a heap buffer over-read occurs.

## Affected products

- Kitware VTK 9.6.1

## Timeline

- 2026-10-29: disclosed

## References

- [https://talosintelligence.com/vulnerability_reports/TALOS-2026-2423](https://talosintelligence.com/vulnerability_reports/TALOS-2026-2423)
- [https://vtk.org/download/](https://vtk.org/download/)

## Related threats

- [VTK vtkWindBladeReader heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-9536-a-heap-based-buffer-overflow-vulnerability-exists-in-the)
- [VTK vtkBMPReader buffer overflow in ExecuteDataWithInformation](https://junglewise.ai/threats/cve-2026-8824-a-memory-corruption-vulnerability-exists-in-the-vtkbmpreader)
- [VTK vtkDEMReader buffer overflow in ReadProfiles](https://junglewise.ai/threats/cve-2026-8822-a-memory-corruption-vulnerability-exists-in-the-vtkdemreader)
- [Kitware VTK invalid pointer dereference in PNG reader](https://junglewise.ai/threats/cve-2026-42057-an-invalid-pointer-dereference-vulnerability-exists-in-the)
- [VTK vtkPNGReader invalid pointer dereference](https://junglewise.ai/threats/cve-2026-41216-an-invalid-pointer-dereference-vulnerability-exists-in-the)