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.
CVE-2026-56820
HIGHPre-NVD 7.47.4—Trending — 3 sources updated this weekElevated
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 78% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.4
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.4Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.4
- EG Score
- 7.4(medium)
- EG Risk
- 64(Attend)EG Risk 64/100SSVC: Attend
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity74% × 45%Exploitation40% × 40%Automatability100% × 15%Action: Remediate soon — notable exploitation risk. - EPSS
- 21.7%
- KEV
- Not listed
Published
July 21, 2026
Last Modified
July 22, 2026
Advisory Details (5)
Auto-updated Jul 22, 2026🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github.
github Patch Available🟡 PoC Available
Missing CertificateID Validation in OCSP Response Allows Replay Attacks · Advisory · netty/netty · GitHub
https://github.com/netty/netty/security/advisories/GHSA-272m-gcwp-mpwggithub_release Patch Available
netty-4.2.16.Final
Patch available: netty/netty netty-4.2.16.Final
https://github.com/netty/netty/releases/tag/netty-4.2.16.Finalgithub_release Patch Available
netty-4.1.136.Final
Patch available: netty/netty netty-4.1.136.Final
https://github.com/netty/netty/releases/tag/netty-4.1.136.Finalgithub_commit Patch Available
commit bb2ff68a1fb7 (netty/netty)
Patch available: netty/netty netty-4.1.136.Final (contains commit bb2ff68a1fb7)
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6github_commit Patch Available
commit 5b68c61f37aa (netty/netty)
Patch available: netty/netty netty-4.2.16.Final (contains commit 5b68c61f37aa)
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003bVendor Advisories for CVE-2026-56820(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
Maven(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| io.netty:netty-handler-ssl-ocsp | 4.1.100.Final ... 4.1.99.Final (50 versions) | 4.1.136.Final | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 9× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-23 14:18 UTCEPSS rescore
- 2026-07-23 03:20 UTCEG score recompute
- 2026-07-22 22:15 UTCEG score recompute
- 2026-07-22 15:08 UTCEG score recompute
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-22 14:04 UTCEG score recompute
- 2026-07-22 01:44 UTCEG score recompute
- 2026-07-21 22:46 UTCEG score recompute
- 2026-07-21 22:44 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-295
Frequently asked(5)
What is CVE-2026-56820?
CVE-2026-56820 is a high vulnerability published on July 21, 2026. 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…
When was CVE-2026-56820 disclosed?
CVE-2026-56820 was first published in the National Vulnerability Database on July 21, 2026, with the most recent update on July 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56820 actively exploited?
CVE-2026-56820 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-56820?
CVE-2026-56820 has a CVSS v3 base score of 7.4 (NVD).
How do I remediate CVE-2026-56820?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56820, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-56820
Is Your Infrastructure Affected by CVE-2026-56820?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.