CVE-2026-56821
Description
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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.
How to fix
- netty netty4.1.136, 4.2.16 or later
- io.netty:netty-handler-ssl-ocsp4.2.16.Final, 4.1.136.Final or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| netty netty | v < 4.1.136, 4.2.0 ≤ v < 4.2.16 | 4.1.136, 4.2.16 |
| io.netty:netty-handler-ssl-ocspMaven | 4.2.0.Final ≤ v < 4.2.16.Final, v < 4.1.136.Final | 4.2.16.Final, 4.1.136.Final |
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Attack Surface Management
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