Vulnerability in Netty
CVE-2026-100665
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.
Vulnerability class: Improper Certificate Validation
Published .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387 (vendor-advisory)
- github.com/netty/netty/commit/09e72c4fd8007277121ed48db63a124b112b96fe (patch)
- github.com/netty/netty/commit/994e887ed9 (patch)
- www.vulncheck.com/advisories/netty-4.2.11-through-4.2.17-quic-hostname-verifica… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-100665?
- CVE-2026-100665 is a high-severity vulnerability in Netty, classified under Improper Certificate Validation. CVSS score: 7.5/10. Published 2026-09-26.
- How severe is CVE-2026-100665?
- High severity. CVSS v3 base score is 7.5 out of 10.