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io.netty:netty-handler-ssl-ocsp

netty

The Netty io.netty netty-handler-ssl-ocsp component's OcspServerCertificateValidator improperly handles out-of-date OCSP responses by flagging them but continuing to treat them as valid. This flaw allows an on-path attacker to replay stale but previously valid OCSP responses, bypassing certificate revocation checks. Additionally, nonce validation is disabled by default, and the freshness check may throw exceptions due to null handling issues. Versions prior to 4.1.136.Final and 4.2.16.Final are affected.

CVE-2026-56821 affects the OcspServerCertificateValidator in the io.netty netty-handler-ssl-ocsp component. The validator flags out-of-date OCSP responses but does not stop processing them, allowing replay of stale yet valid OCSP responses. This bypasses revocation checks for certificates that have been revoked. Nonce validation is off by default, reducing protection against replay attacks. The freshness check may also throw exceptions due to null handling issues. The vulnerability affects Netty versions prior to 4.1.136.Final and 4.2.16.Final, with multiple specific affected versions identified. The CVSS 3.1 score is 7.4 (medium severity), reflecting network attack vector, high complexity, no privileges required, no user interaction, unchanged scope, and high impact on confidentiality and integrity.

Detailed information about Io.netty:netty handler ssl ocsp: Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator (CVE-2026-56821) affect

Io.netty:netty handler ssl ocsp: Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator (CVE-2026-56821) - Live Threat Intelligence - Threat Radar | OffSeq.com

Netty: Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing… (CVE-2026-56821)

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