Netty prior 4.1.136.Final/4.2.16.Final OcspServerCertificateValidator OcspServerCertificateValidator.java certificate validation

Summaryinfo

A vulnerability was found in Netty. It has been rated as problematic. This impacts the function io.netty.handler.ssl.ocsp.OcspServerCertificateValidator.userEventTriggered of the file io/netty/handler/ssl/ocsp/OcspServerCertificateValidator.java of the component OcspServerCertificateValidator. The manipulation leads to certificate validation. This vulnerability is documented as CVE-2026-56822. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Netty. This issue affects the function io.netty.handler.ssl.ocsp.OcspServerCertificateValidator.userEventTriggered of the file io/netty/handler/ssl/ocsp/OcspServerCertificateValidator.java of the component OcspServerCertificateValidator. The manipulation with an unknown input leads to a certificate validation vulnerability. Using CWE to declare the problem leads to CWE-295. The product does not validate, or incorrectly validates, a certificate. Impacted is integrity. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-56822 since 06/23/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1587.003 for this issue.

Upgrading to version 4.1.136.Final or 4.2.16.Final eliminates this vulnerability.

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Productinfo

Name

• Netty

Website

• Product: https://github.com/netty/netty/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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