9.1

CVE-2026-56820: netty Improper Certificate Validation

CVSS: 9.1v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-56820DEBIAN-CVE-2026-56820CGA-43vx-478j-j998
Published 21-07-2026Last modified 24-07-2026
Open JSON

Vulnerability summary

CVE-2026-56820 is a critical (CVSS 9.1) Improper Certificate Validation vulnerability in netty. EPSS estimates a 0.31% chance of exploitation in the next 30 days, higher than 22.7% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (NVD)
EPSS score
0.31%
0%100%
Low · +0.09 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-GW2R-J93G-42H4

Timeline

  1. 21-07-2026
    PublishedVulnerability first disclosed.
  2. 24-07-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

0.31%

Chance of exploitation in the next 30 days

Percentile

23%

Versus all other CVEs

30-day change

+0.09 pp

From 0.22% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.31%

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≥ 4.2.0.Final, < 4.2.16.Final | < 4.1.136.Final | < 4.1.136 | ≥ 4.2.0, < 4.2.16
Ubuntu1 product
  • nettyAll versions (No fix recorded)

6 vendors · 25 products

References

11 links
Show all 11 references