CVE-2026-56821

Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator

Published Jul 28, 2026 CVSS 3.1 · 7.4 High EPSS < 1% KEV · Not listed
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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.

Analysis

No analysis available yet

Remediation

No remediation available yet

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-g7hg-vrcf-mvmr Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A flaw was found in netty-handler-ssl-ocsp, a component of the Netty network application framework. The Online Certificate Status Protocol (OCSP) stapling validator in this component does not properly check certificate revocation status. This can allow an attacker to use revoked certificates without detection, potentially compromising secure communications. 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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.
Title io.netty/netty-handler-ssl-ocsp: Netty: Improper certificate revocation check in netty-handler-ssl-ocsp Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator
Weaknesses CWE-299
References
Metrics cvssV3_1

{'score': 5.7, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'}

cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'}

Type Values Removed Values Added
Description A flaw was found in netty-handler-ssl-ocsp, a component of the Netty network application framework. The Online Certificate Status Protocol (OCSP) stapling validator in this component does not properly check certificate revocation status. This can allow an attacker to use revoked certificates without detection, potentially compromising secure communications.
Title io.netty/netty-handler-ssl-ocsp: Netty: Improper certificate revocation check in netty-handler-ssl-ocsp
Weaknesses CWE-93
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.7, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'}

threat_severity

Moderate

Weaknesses
  • CWE-299

    Improper Check for Certificate Revocation

  • CWE-93

    Improper Neutralization of CRLF Sequences ('CRLF Injection')

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 31, 2026, 4:12 PM
Reserved
Jun 23, 2026, 2:55 PM
Status
Analyzed
Published
Jul 29, 2026, 12:16 AM
Modified
Aug 7, 2026, 3:05 PM
Severity
Moderate
Public date
Jul 9, 2026, 12:00 AM