CVE-2026-56821
7.4 · HIGHOverview
CVE-2026-56821 is a high-severity vulnerability affecting netty netty. It was published on July 29, 2026 and has a CVSS 3.1 base score of 7.4 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.4, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.
Remediation
Check the references section for vendor advisories and patches from netty. Update netty to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| netty | netty | >= 0, < 4.1.136 | Affected |
Frequently Asked Questions
What is CVE-2026-56821?
CVE-2026-56821 is a high-severity vulnerability affecting netty netty. It was published on July 29, 2026 and has a CVSS 3.1 base score of 7.4 (HIGH).
How severe is CVE-2026-56821?
This vulnerability has a CVSS 3.1 base score of 7.4, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-56821?
Check the references section for vendor advisories and patches from netty. Update netty to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-56821?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-56821 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
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