Skip to content
Fencer Intel
high 7.4

CVE-2026-56821 json

Netty: Out-of-date OCSP Responses Accepted by OcspServerCertificateValidator

published 3mo ago modified 2mo ago also EUVD-2026-50090 , GHSA-g7hg-vrcf-mvmr

cvss
7.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits
0
none known

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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD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

Patch / fix

  • maven io.netty:netty-handler-ssl-ocsp 4.1.136.Final, 4.2.16.Final
  • io.netty netty-handler-ssl-ocsp 4.1.136.Final, 4.2.16.Final
  • netty netty 4.1.136.Final, 4.2.16.Final
  • netty-tcnative SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 2.0.80-150200.3.48.1
  • netty SLE Module for Package Hub 15 SP7 4.1.136-150200.4.53.1

suse advisories SUSE-SU-2026:3482-1

  • netty openSUSE Tumbleweed 4.1.136-1.1

opensuse advisories openSUSE-SU-2026:11394-1

Is CVE-2026-56821 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-56821 updated cvss 5.7

io.netty/netty-handler-ssl-ocsp: Netty: Improper certificate revocation check in netty-handler-ssl-ocsp

  • Red Hat build of Apache Camel for Spring Boot 4 netty-handler-ssl-ocsp 4.1.135.Final-redhat-00001 Red Hat Data Grid 8 netty-handler-ssl-ocsp 4.1.135.Final-redhat-00001 Red Hat JBoss Enterprise Application Platform Expansion Pack netty-handler-ssl-ocsp 4.1.135.Final-redhat-00001
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
3mo ago

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/netty/netty/security/advisories/GHSA-g7hg-vrcf-mvmr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
GitHub 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
maven io.netty:netty-handler-ssl-ocsp
>=4.2.0.Final, <4.2.16.Final
<4.1.136.Final
4.2.16.Final
4.1.136.Final

Affected products

  • netty netty

Classification

Weakness
  • CWE-299 Improper Check for Certificate Revocation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.