CVE-2026-56821

Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator

State: Published
Severity: 7.4 High
Published: Jul 28, 2026
Updated: Jul 31, 2026
Reserved: Jun 23, 2026

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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.

Scores

CVSS	Score	Vector	Source
3.1	7.4 High	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N	GitHub_M

Weaknesses

CWE-299 Improper Check for Certificate Revocation

Affected Products

Product	Versions
nettynetty	< 4.1.136.FinalAffected >= 4.2.0.Final, < 4.2.16.FinalAffected

References

https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr

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