Vulnerability in Netty
CVE-2026-62243
Netty (io.netty:netty-handler) versions from 4.2.0.Final through 4.2.16.Final and versions through 4.1.136.Final disable TLS hostname verification on the SslProvider.OPENSSL client path when a plain (non-extended) X509TrustManager is used and Unsafe-based trust-manager wrapping is unavailable (Java 25+). In this configuration the OpenSSL client does not perform hostname verification, allowing a man-in-the-middle attacker to present a certificate issued for a different hostname that is accepted without validation. Fixed in 4.2.17.Final and 4.1.137.Final.
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: 0.002 (4.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 4th percentile — 4.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/netty/netty/security/advisories/GHSA-p85m-gvr3-788c (vendor-advisory)
- www.vulncheck.com/advisories/netty-through-tls-hostname-verification-bypass (third-party-advisory)
Frequently asked questions
- What is CVE-2026-62243?
- CVE-2026-62243 is a high-severity vulnerability in Netty, classified under Improper Validation of Certificate with Host Mismatch. CVSS score: 7.5/10. Published 2026-08-22.
- How severe is CVE-2026-62243?
- High severity. CVSS v3 base score is 7.5 out of 10.