CVE-2026-56820 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-56820CRITICAL

Netty: Missing CertificateID Validation in OCSP Response Allows Replay Attacks

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  H  N    9.1   .0018    8.1     —

AFFECTED
  Product  Versions                          Fixed
  netty    >= 4.2.0.Final, < 4.2.16.Final –  —

TIMELINE
  Jun 23  Reserved by GitHub_M
  Jul 21  EXPLOIT PUBLISHED — CVE-2026-56820 (netty). Public exploit reference added.
  Jul 21  Published (CNA: GitHub_M)
  Jul 30  EXPLOIT PUBLISHED — CVE-2026-56820 (netty). Public exploit reference added.

CWE-295 · CNA: GitHub_M · CVSS v3.1 · 5 references · NVD status: Analyzed

Description

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and prior to 4.1.135.Final, `OcspClient` does not validate that the `CertificateID` in an OCSP response matches the requested `CertificateID`, which can lead to replay attack. `OcspClient.validateResponse` accepts a legitimately signed `GOOD` status response for an unrelated certificate issued by the same CA, allowing bypass of revocation checks for another certificate. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
June 23, 2026	Reserved	Reserved by GitHub_M
July 21, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-56820 (netty). Public exploit reference added.
July 21, 2026	Published	Published (CNA: GitHub_M)
July 30, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-56820 (netty). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
netty	netty	—	>= 4.2.0.Final, < 4.2.16.Final	—

Weaknesses

CWE-295

References (5)

https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b [Patch]
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6 [Patch]
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final [Release Notes]
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final [Release Notes]
https://github.com/netty/netty/security/advisories/GHSA-272m-gcwp-mpwg [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-56820 at cve.org

Vendors: netty

Weaknesses: CWE-295

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-56820 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.