CVE-2026-56821
Published:July 28, 2026
Updated:August 04, 2026
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response to bypass revocation of a since-revoked certificate. Exploitation can lead to certificate revocation bypass via replay of an expired OCSP response. Any application using OcspServerCertificateValidator is affected; a revoked certificate can be accepted. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
Affected Packages
io.netty:netty-handler-ssl-ocsp (JAVA):
Affected version(s) >=4.1.86.Final <4.1.136.FinalFix Suggestion:
Update to version 4.1.136.Finalio.netty:netty-handler-ssl-ocsp (JAVA):
Affected version(s) >=4.2.0.Final <4.2.16.FinalFix Suggestion:
Update to version 4.2.16.FinalRelated Resources (6)
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Contact UsCVSS v4
Base Score:
9.1
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.4
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
Improper Check for Certificate Revocation
EPSS
Base Score:
0.14