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TI-2026-40974 Aliases CVE-2026-56821GHSA-g7hg-vrcf-mvmr

Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator

Priority HIGH 68CWE-299Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Partial Red Hat: 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD response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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00219 12th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial netty (netty): 4.1.136.Final, 4.2.16.Finalio.netty:netty-handler-ssl-ocsp (Maven): 4.2.16.Final, 4.1.136.FinalRed Hat: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
nettynettybefore 4.1.136.Final; 4.2.0.Final to before 4.2.16.Final4.1.136.Final, 4.2.16.FinalPatch availableCNA
—io.netty:netty-handler-ssl-ocsp (Maven)4.2.0.Final to before 4.2.16.Final4.2.16.FinalPatch availableGHSA-g7hg-vrcf-mvmr
—io.netty:netty-handler-ssl-ocsp (Maven)before 4.1.136.Final4.1.136.FinalPatch availableGHSA-g7hg-vrcf-mvmr
  • netty Vendornetty Affected before 4.1.136.Final; 4.2.0.Final to before 4.2.16.Final Fixed in 4.1.136.Final, 4.2.16.Final Patch available CNA
  • io.netty:netty-handler-ssl-ocsp (Maven) Vendor— Affected 4.2.0.Final to before 4.2.16.Final Fixed in 4.2.16.Final Patch available GHSA-g7hg-vrcf-mvmr
  • io.netty:netty-handler-ssl-ocsp (Maven) Vendor— Affected before 4.1.136.Final Fixed in 4.1.136.Final Patch available GHSA-g7hg-vrcf-mvmr

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*before 4.1.136; 4.2.0 to before 4.2.16Vulnerablenetty
  • cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:* Versions before 4.1.136; 4.2.0 to before 4.2.16 Vulnerable ·netty

Remediation

  • Fix · CNA netty (netty) Fixed in 4.1.136.Final, 4.2.16.Final
  • Fix · GHSA-g7hg-vrcf-mvmr io.netty:netty-handler-ssl-ocsp (Maven) Fixed in 4.2.16.Final Advisory →
  • Fix · GHSA-g7hg-vrcf-mvmr io.netty:netty-handler-ssl-ocsp (Maven) Fixed in 4.1.136.Final Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Data Grid 8AffectedNo fix yet: Fix deferred
Red Hat JBoss Enterprise Application Platform Expansion PackAffectedNo fix yet: Fix deferred
Red Hat build of Apache Camel for Spring Boot 4AffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-56821
  2. 2026-10-03 Alias added: GHSA-g7hg-vrcf-mvmr

References

Exploit 1

Other 3

  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2026-30861 Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization CVSS 3.1CRITICAL 9.8
  • TI-2026-30864 Netty: HttpClientCodec response desynchronization CVSS 3.1CRITICAL 9.1
  • TI-2026-30859 Netty: DNS Codec Input Validation Bypass in Netty (Encoder + Decoder) CVSS 3.1CRITICAL 9.1
  • TI-2026-40973 Netty: Missing CertificateID Validation in OCSP Response Allows Replay Attacks CVSS 3.1CRITICAL 9.1
  • TI-2026-40972 Uncontrolled resource consumption in netty CVSS 3.1HIGH 7.5
See all 92 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences