High severity · published Sep 26, 2026
CVE-2026-100665
Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
netty · netty
4.2.11.Final before 4.2.18.Final · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-100665
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-100665
vendor-advisory
https://github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387
patch
https://github.com/netty/netty/commit/09e72c4fd8007277121ed48db63a124b112b96fe
patch
https://github.com/netty/netty/commit/994e887ed9
third-party-advisory
https://www.vulncheck.com/advisories/netty-4.2.11-through-4.2.17-quic-hostname-verification-bypass
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