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CVE-2026-56822
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 forwards the SslHandshakeCompletionEvent before the asynchronous OCSP validation completes. This allows the client's downstream handlers to send sensitive application data (e.g., HTTP requests) to a revoked server before the channel is closed by the OCSP check. n io.netty.handler.ssl.ocsp.OcspServerCertificateValidator#userEventTriggered, when an SslHandshakeCompletionEvent is received, the validator immediately calls ctx.fireUserEventTriggered(evt). It then initiates an asynchronous OCSP query using OcspClient.query. Because the handshake completion event is forwarded immediately, downstream handlers in the client's pipeline are notified that the TLS handshake is successful. They may then begin reading and processing incoming application data or sending outgoing data. If the OCSP response later indicates the server's certificate is REVOKED, the validator closes the channel, but by this time, the client may have already leaked sensitive data to a revoked server or processed malicious responses from it. 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) >=4.2.0.Final <4.2.16.Final
Fix Suggestion:
Update to version 4.2.16.Final
io.netty:netty-handler-ssl-ocsp (JAVA):
Affected version(s) >=4.1.86.Final <4.1.136.Final
Fix Suggestion:
Update to version 4.1.136.Final
io.netty:netty-handler-ssl-ocsp (JAVA):
Affected version(s) >=4.1.86.Final <4.1.136.Final
Fix Suggestion:
Update to version 4.1.136.Final
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CVSS 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)
Time-of-check Time-of-use (TOCTOU) Race Condition
EPSS
Base Score:
0.11