7.4

CVE-2026-56821: netty

CVSS: 7.4v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-56821DEBIAN-CVE-2026-56821CGA-2fmj-m796-mfr7
Published 28-07-2026Last modified 31-07-2026
Open JSON

Vulnerability summary

CVE-2026-56821 is a high (CVSS 7.4) vulnerability in netty. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.5% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
40/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.4/10
010
High · v3.1 (CVE.org)
EPSS score
0.22%
0%100%
Low · +0.06 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1github

Advisory lineage

Upstream 0 · Downstream 2 · Related 3
OPENSUSE-SU-2026:11394-1SUSE-SU-2026:3482-1CGA-CHVG-88HC-9HG6

Timeline

  1. 28-07-2026
    PublishedVulnerability first disclosed.
  2. 31-07-2026
    Last modifiedVulnerability information updated.

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 Prior to versions 4.1.136.Final and 4.2.16.Final, the OcspServerCertificateValidator flags an out-of-date OCSP response but does not stop processing it, so an expired GOOD response is still reported as VALID, letting an on-path attacker replay a stale GOOD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

7 scores · 7 sources · 1 version

EPSS trend

Probability

0.22%

Chance of exploitation in the next 30 days

Percentile

12%

Versus all other CVEs

30-day change

+0.06 pp

From 0.16% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.22%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • githubUnverified

    Netty

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Chainguard16 products
  • apache-hop< 2.18.1-r7
  • apache-hop-fips< 2.18.1-r5
  • cassandra-5.0< 5.0.8-r12
  • cassandra-fips-5.0< 5.0.8-r7
  • gremlin-server< 3.8.1-r2
Wolfi5 products
  • cassandra-5.0< 5.0.8-r12
  • management-api-for-apache-cassandra-5.0< 0.1.122-r2
  • tez< 0.10.5-r21
  • thingsboard-tb-mqtt-transport< 4.3.1.3-r6
  • thingsboard-tb-node< 4.3.1.3-r6
Debian1 product
  • nettyAll versions (No fix recorded)
Io.netty1 product
  • netty-handler-ssl-ocsp≥ 4.2.0.Final, < 4.2.16.Final | < 4.1.136.Final
Netty1 product
  • netty< 4.1.136.Final | ≥ 4.2.0.Final, < 4.2.16.Final | < 4.1.136 | ≥ 4.2.0, < 4.2.16
Ubuntu1 product
  • nettyAll versions (No fix recorded)

6 vendors · 25 products

References

9 links