---
cve: "CVE-2026-100665"
severity: "HIGH"
cvss: 8.7
epss: "0.3%"
vendor: "netty"
kev: false
exploited: false
published: "2026-09-26 14:16:49"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-10-01T09:21:23+02:00"
---

# CVE-2026-100665

> 8.7 HIGH · 🧪 PoC

## Beschreibung

Netty versions from 4.2.11.Final before 4.2.18.Final contain an incomplete hostname verification fix in the QUIC certificate verification path when using a plain X509TrustManager. The BoringSSLCertificateVerifyCallback discards the SSLEngine for plain trust managers, preventing endpoint identification from running even when HTTPS verification is configured. Attackers on the network path can present a certificate chain for the wrong hostname that the plain trust manager accepts, bypassing hostname authentication for QUIC clients.

## CNA-Record (Kanon, cvelistV5)

- CNA: **VulnCheck**
- State: PUBLISHED
- Stand: 2026-09-27 16:27:50
- CNA-CVSS: **8.7** (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- 2521f494432e27415a567d3a81a9eb907abf20b3 (Commit)
- 09e72c4fd8007277121ed48db63a124b112b96fe (Commit)

## BSI-Hinweise (deutsch)

- [Netty: Mehrere Schwachstellen](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-3291) — _BSI-Einstufung: hoch_
  Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Netty ausnutzen, um Denial-of-Service-Zustände zu verursachen, Sicherheitsmaßnahmen zu umgehen, Request- oder Response-Smuggling durchzuführen sowie Daten offenzulegen oder zu manipulieren.

## Referenzen

- <https://github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387>
- <https://github.com/netty/netty/commit/09e72c4fd8007277121ed48db63a124b112b96fe>
- <https://github.com/netty/netty/commit/994e887ed9>
- <https://www.vulncheck.com/advisories/netty-4.2.11-through-4.2.17-quic-hostname-verification-bypass>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-100665) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_