{"id":"CVE-2026-56821","aliases":["GHSA-g7hg-vrcf-mvmr"],"url":"https://o3.security/vulnerability/CVE-2026-56821","summary":"Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator","details":"Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.","published":"2026-07-28T23:07:13.616Z","modified":"2026-08-12T03:51:17.346421310Z","cvss":{"score":7.4,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":{"score":0.00164,"percentile":0.05884,"asOf":"2026-09-06"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Maven","name":"io.netty:netty-handler-ssl-ocsp","fixedVersion":"4.2.16.Final"},{"ecosystem":"Maven","name":"io.netty:netty-handler-ssl-ocsp","fixedVersion":"4.1.136.Final"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56821.json"},{"type":"ADVISORY","url":"https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56821"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:17.346421310Z"}}