EUVD-2026-64271
GHSA-c3j3-64rf-grvf
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
MitM network position plus three simultaneous configuration prerequisites (OPENSSL provider, plain TrustManager, Java 25+) justify AC:H; no auth required on attacker side and confidentiality-only impact.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
3DescriptionCVE.org
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.
AnalysisAI
TLS hostname verification is silently bypassed in Netty's OpenSSL client path, allowing a network man-in-the-middle attacker to intercept encrypted communications by presenting a certificate issued for a different hostname. Affected are applications using io.netty:netty-handler versions 4.2.0.Final through 4.2.16.Final or any 4.1.x through 4.1.136.Final, specifically when the SslProvider.OPENSSL client path is configured with a plain X509TrustManager and running on Java 25 or later, where Unsafe-based trust-manager wrapping is unavailable. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Three configuration conditions on the vulnerable application must all be true simultaneously: (1) the Netty SSL pipeline must be configured with SslProvider.OPENSSL on the client side, not the default SslProvider.JDK; (2) the trust manager supplied must be a plain X509TrustManager rather than the extended X509ExtendedTrustManager, which retains the hostname-check hook; (3) the JVM must be Java 25 or later, where Unsafe-based reflection used to inject hostname verification into the native OpenSSL path is unavailable. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The provided CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H) scores 8.7 and treats this as a straightforward high-severity network vulnerability, but the real-world attack complexity is meaningfully higher than AC:L implies. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: 4.2.17.Final and 4.1.137.Final. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all applications using affected Netty versions (4.1.0-4.1.136.Final or 4.2.0-4.2.16.Final) on Java 25+ with OpenSSL provider and plain X509TrustManager configuration. …
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