---
cve: "CVE-2026-44452"
severity: "MEDIUM"
cvss: 5.9
epss: "25%"
vendor: "h2o"
kev: false
exploited: false
published: "2026-07-16 23:16:17"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-02T11:08:42+02:00"
---

# CVE-2026-44452

> 5.9 MEDIUM · 🧪 PoC

## Beschreibung

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is NULL-terminated. This is a potential denial-of-service attack vector in sense that it might trigger segmentation violation. This issue has been fixed by commit 8dc37cb.

## CVSS-Vektor

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

| 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 | Keine | good |
| I Integrität | Keine | good |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- 8dc37cb1e6171f7f772667618ea440696fed82c3 (Commit)

## Referenzen

- <https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq>
- <https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-44452) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_