---
id: "CVE-2026-9535"
kind: "vulnerability"
aliases: ["CVE-2026-9535"]
title: "VTK: crafted Chaco file triggers out-of-bounds read in reader"
severity: "high"
cvss: 8.2
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "vtk", "fixed": [], "affected": "9.6.1", "ecosystem": "vendor"}]
ecosystems: []
tags: ["c++", "package", "scientific-computing", "vtk"]
not_affected_if: ["no-chaco-input", "not-version-9.6.1", "trusted-files-only"]
published_at: "2026-10-29T19:17:29+00:00"
first_seen_at: "2026-10-29T19:26:48+00:00"
updated_at: "2026-10-29T19:28:23+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9535", "first_seen_at": "2026-10-29T19:26:48+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-29T19:28:23+00:00"}]
---

# VTK: crafted Chaco file triggers out-of-bounds read in reader

The Visualization Toolkit (VTK) 9.6.1 has an out-of-bounds read in its vtkChacoReader InputGraph2 code path. A specially crafted Chaco graph file can make the reader read memory outside its buffer, and an attacker can exploit this by supplying a malicious file.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:vtk affected 9.6.1 fixed ?

## How to check

- Check the installed VTK version, for example `vtkVersion` in your build or the package manager listing, and look for `9.6.1`.
- Search your code and pipelines for use of `vtkChacoReader` or InputGraph2 reading untrusted Chaco files.

## Timeline

- 2026-10-29T19:26:48+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-9535
- 2026-10-29T19:28:23+00:00 analyst — No Talos/VTK advisory found yet; only NVD (Talos CNA) text. vtkChacoReader::InputGraph2 exists in VTK 9.6 docs (linked). VTK 9.6.2 was released 2026-05-18 but no source says it fixes this; fix unknown. Not exploited, no PoC found. Settle by reading the Talos report or the VTK GitLab issue.

## Documents

- [describes] VTK: vtkChacoReader Class Reference (9.6) https://vtk.org/doc/nightly/release/9.6/html/classvtkChacoReader.html

## From the sources

A out-of-bounds read vulnerability exists in the vtkChacoReader InputGraph2 functionality of vtk (version(s): 9.6.1). A specially crafted chaco can lead to an out-of-bounds read. An attacker can provide a malicious file to trigger this vulnerability.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_