---
cve: "CVE-2026-86251"
severity: "MEDIUM"
cvss: 5.9
epss: "3.2%"
vendor: "Generic Security"
kev: false
exploited: false
published: "2026-09-06 12:17:15"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-06T20:05:55+02:00"
---

# CVE-2026-86251

> 5.9 MEDIUM

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Keine | good |
| A Verfügbarkeit | Keine | good |

## Referenzen

- <https://github.com/h3js/h3/security/advisories/GHSA-72gr-qfp7-vwhw>
- <https://www.vulncheck.com/advisories/h3-before-1.15.9-path-traversal-via-double-decoding>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-86251) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_