---
id: CVE-2026-86251
title: >-
  h3 versions before 1.15.9 contain a path traversal vulnerability in the
  serveStatic utility
summary: >-
  h3 versions before 1.15.9 contain a path traversal vulnerability in the
  serveStatic utility. A double-decoding flaw allows a request path containing
  double-encoded dot sequences (e.g. %252e%252e) to be decoded to %2e%2e, which
  survives r…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-22
vendor: h3js
product: h3
affected:
  - h3 < 1.15.9
published: '2026-09-06'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T14:17:21.977'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86251'
references:
  - url: 'https://github.com/h3js/h3/security/advisories/GHSA-72gr-qfp7-vwhw'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/h3-before-1.15.9-path-traversal-via-double-decoding
    label: disclosure@vulncheck.com
  - url: 'https://github.com/h3js/h3/security/advisories/GHSA-72gr-qfp7-vwhw'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86251.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-86251'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2529161'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-86251'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86251'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-09T13:57:13.508362Z'
epss: 0.00428
epssPercentile: 0.3439
ingestedAt: '2026-09-07T04:04:50.495Z'
---

## Overview

h3 versions before 1.15.9 contain a path traversal vulnerability in the serveStatic utility. A double-decoding flaw allows a request path containing double-encoded dot sequences (e.g. %252e%252e) to be decoded to %2e%2e, which survives resolveDotSegments() because that function only checks for literal '.' characters. When the resulting asset ID is resolved by URL-based backends (CDN, S3, object storage), %2e%2e is interpreted as '..' per RFC 3986, enabling path traversal to read arbitrary files from the backend.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · 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-2026-86251.json)