---
cve: "CVE-2026-75595"
severity: "CRITICAL"
cvss: 9.1
epss: "32%"
vendor: "netty"
kev: false
exploited: false
published: "2026-08-19 21:17:37"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-05T22:54:57+02:00"
---

# CVE-2026-75595

> 9.1 CRITICAL · 🧪 PoC

## Beschreibung

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/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)

- 5471f0a6ffa4ab39db22c468c6c851af4ecae709 (Commit)
- e0789d32c72f46fd2e7c99b6fdbbf7e2f4409e44 (Commit)

## Referenzen

- <https://github.com/netty/netty/security/advisories/GHSA-c4c3-7fpv-j4q5>
- <https://github.com/netty/netty/pull/17213>
- <https://github.com/netty/netty/pull/17217>
- <https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7>
- <https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961>
- <https://github.com/netty/netty/releases/tag/netty-4.1.137.Final>
- <https://github.com/netty/netty/releases/tag/netty-4.2.17.Final>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-75595) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_