{"cve":"CVE-2026-56821","nvd":{"published":"2026-07-29T00:16:38.573","modified":"2026-08-07T15:05:53.920","status":"Analyzed","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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","score":7.4},"cwes":["CWE-299"],"references":["https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr","https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr"],"products":["netty:netty"],"source":"nvd","synced_at":"2026-10-19T22:46:40.600842820+00:00"},"epss":{"cve":"CVE-2026-56821","score":0.00219,"percentile":0.12428,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-g7hg-vrcf-mvmr","url":"https://osv.dev/vulnerability/GHSA-g7hg-vrcf-mvmr","summary":"Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator","modified":"2026-09-10T03:50:52.144967568Z","packages":[{"ecosystem":"Maven","name":"io.netty:netty-handler-ssl-ocsp","purl":"pkg:maven/io.netty/netty-handler-ssl-ocsp","ranges":[">=4.2.0.Final <4.2.16.Final"],"fixed":["4.2.16.Final"]},{"ecosystem":"Maven","name":"io.netty:netty-handler-ssl-ocsp","purl":"pkg:maven/io.netty/netty-handler-ssl-ocsp","ranges":["<4.1.136.Final"],"fixed":["4.1.136.Final"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}