Is CVE-2026-56820 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-56820?

CVE-2026-56820 has a CVSS v3 severity of HIGH (7.4).

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CVE-2026-56820

Description

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and prior to 4.1.135.Final, `OcspClient` does not validate that the `CertificateID` in an OCSP response matches the requested `CertificateID`, which can lead to replay attack. `OcspClient.validateResponse` accepts a legitimately signed `GOOD` status response for an unrelated certificate issued by the same CA, allowing bypass of revocation checks for another certificate. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.