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CVE-2026-56820VulnerabilityPublished Updated

Netty:

Affects nettySource GCVE Database

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Not known to be exploited · CVSS 9.1 Critical · fixed in 4.1.136 : patch netty as a priority.

Data as of 9 Nov 2026, 14:17 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 4.1.136
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 21 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10nettypkg:deb/ubuntu/netty?arch=source&distro=stonkingOther threatsAffected
  • =1:4.1.48-16
  • =1:4.1.48-16ubuntu1
Fixed in–
Ubuntu Pro 26.04 LTSnettypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/resoluteOther threatsAffected
  • 1:4.1.48-10 – 1:4.1.48-16ubuntu0.1~esm2
7 affected builds
Fixed in–
Ubuntu Pro 24.04 LTSnettypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/nobleOther threatsAffected
  • 1:4.1.48-7 – 1:4.1.48-9ubuntu0.2+esm2
11 affected builds
Fixed in–
Ubuntu Pro 22.04 LTSnettypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/jammyOther threatsAffected
  • 1:4.1.48-4 – 1:4.1.48-4+deb11u2ubuntu0.2+esm1
10 affected builds
Fixed in–
Ubuntu Pro 18.04 LTSnettypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/bionicOther threatsAffected
  • 1:4.1.7-4 – 1:4.1.7-4ubuntu0.1~esm1
10 affected builds
Fixed in–
Ubuntu Pro 16.04 LTSnettypkg:deb/ubuntu/netty?arch=source&distro=esm-apps-legacy/xenialOther threatsAffected
  • 1:3.2.6.Final-2 – 1:4.0.34-1ubuntu0.1~esm5
9 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Netty to version 4.1.136.Final or later, or 4.2.16.Final or later, where this vulnerability is fixed. No other mitigations are indicated by the vendor advisory.

Description

Netty versions 4.2.0.Final through 4.2.15.Final and versions prior to 4.1.135.Final contain a vulnerability in the OcspClient component where it does not properly validate that the CertificateID in an OCSP response matches the requested CertificateID. This flaw allows an attacker to bypass revocation checks by replaying a legitimately signed 'GOOD' status response for a different certificate issued by the same CA. The issue is resolved in versions 4.1.136.Final and 4.2.16.Final.

References

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