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VULNERABILITIES

CVE-2026-56821 Details

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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD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

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:7.4 HIGHVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr CISA-ADPExploitVendor Advisory
https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr [email protected]ExploitVendor Advisory

Weakness Enumeration

CWE-IDCWE NameSource
CWE-299Improper Check for Certificate Revocation[email protected]

Affected Products

ProductVersions
netty netty
< 4.1.136
>= 4.2.0, < 4.2.16

CPE

  • cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*

Remediation

  • No remediation found in references.

Change History

7 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-56821
NVD Published Date:
Jul 29, 2026
NVD Last Modified:
Aug 7, 2026
Source:
[email protected]
CVE-2026-56821 Details - Not Deferred