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 · last modified .
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
EPSS: 0.004 (30.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 30.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
Weakness classification (CWE)
References
- GitHub Security Advisory (GHSA-mj35-3qqm-q387) (vendor-advisory)
- Patch Commit (patch)
- Patch Commit (patch)
- VulnCheck Advisory: Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass (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.