8.7

CVE-2026-100665: netty Improper Certificate Validation

CVSS: 8.7v4.0HighDeferred
AliasesUBUNTU-CVE-2026-100665
Published 26-09-2026Last modified 02-10-2026
Open JSON

Vulnerability summary

CVE-2026-100665 is a high (CVSS 8.7) Improper Certificate Validation vulnerability in netty. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 20.3% of scored vulnerabilities.

Overall risk
35/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.7/10
010
High · v4.0 (CVE.org)
EPSS score
0.29%
0%100%
Low · Change unavailable
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 26-09-2026
    PublishedVulnerability first disclosed.
  2. 02-10-2026
    Last modifiedVulnerability information updated.

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 metrics

6 scores · 3 sources · 2 versions

EPSS trend

Probability

0.29%

Chance of exploitation in the next 30 days

Percentile

20%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

27-09-202620-10-2026
EPSS score
0.29%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Netty1 product
  • netty≥ 4.2.11.Final, < 4.2.18.Final
Ubuntu1 product
  • nettyAll versions (No fix recorded)

2 vendors · 2 products

References

6 links