CVE-2026-56821
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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.
Scoring
- Severity
- HIGH
- CVSS base score
- 7.4
- CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- EPSS probability
- 0.16%
- CWE
- CWE-299
- Published
- 2026-07-28
- Last modified
- 2026-07-31
Affected products
- netty netty
- netty netty
- netty netty
Weakness type
Related vulnerabilities
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- CVE-2026-9636 — Rockwell Automation CompactLogix® 5380 ControlLogix® 5580 / 1756-EN4 Communications Module – Certificate Revocation List Vulnerability
- CVE-2026-6899 — Improper Check for Certificate Revocation in S2OPC
- CVE-2026-4428 — CRL Distribution Point Scope Check Logic Error in AWS-LC
- CVE-2025-11955 — Incorrect validation of OCSP certificates in TheGreenBow VPN Client Windows Enterprise
- CVE-2025-36057 — IBM Cognos Analytics Mobile (iOS) authentication bypass
- CVE-2025-3085 — MongoDB Server running on Linux may allow unexpected connections where intermediate certificates are revoked