---
id: CVE-2026-86250
title: >-
  h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from
  user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie()
  functions
summary: >-
  h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from
  user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie()
  functions. Attackers can send a crafted cookie header with an extremely large
  chunk…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-606
vendor: Red Hat
product: Red Hat OpenShift AI (RHOAI)
affected:
  - openshift_ai_rhoai
published: '2026-09-06'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T18:17:18.657'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86250'
references:
  - url: 'https://github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unbounded-chunked-cookie
    label: disclosure@vulncheck.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86250.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-86250'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2529162'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-86250'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86250'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00488
epssPercentile: 0.39312
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-18T17:07:52.002310Z'
ingestedAt: '2026-09-07T03:04:07.576Z'
---

## Overview

h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat OpenShift AI (RHOAI) · no fix planned: Red Hat OpenShift AI (RHOAI) · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86250.json)