---
id: CVE-2026-89087
title: The cstruct package before 6.3.0 for OCaml mishandles indexes.
summary: The cstruct package before 6.3.0 for OCaml mishandles indexes.
severity: high
cvss: 7.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L'
cwe:
  - CWE-573
vendor: OCaml
product: cstruct
affected:
  - cstruct < 6.3.0
published: '2026-09-10'
updated: '2026-09-22'
sourceUpdated: '2026-09-22T20:00:03.713'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89087'
references:
  - url: 'https://osv.dev/vulnerability/OSEC-2026-20'
    label: cve@mitre.org
tags:
  - nvd
  - cve.org
epss: 0.00188
epssPercentile: 0.08613
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-14T15:36:00.424159Z'
ingestedAt: '2026-09-14T02:45:19.038Z'
---

## Overview

The cstruct package before 6.3.0 for OCaml mishandles indexes.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.