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CVE-2026-56817 Netty

Affected softwareNetty
Severity8.3 High CVSS 4.0 2 scores
Fixed in4.2.16.Final, 4.1.136.Final
WeaknessXML external entity (XXE) (CWE-611)
Published21 Jul 2026
Updated30 Jul 2026

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 4.1.0.Final through 4.1.135.Final, any caller that can deliver bytes to a Netty channel pipeline containing XmlDecoder can send XML with a DOCTYPE declaration to an AsyncXMLInputFactory instantiated with no security configuration, leaving DTD and entity handling active depending on Aalto XML async parser behavior and creating conditional XML external entity risk. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment exploitation: none
  • Indexed PoC none indexed
  • EPSS 0.69% chance in 30 days

Waratek protection

Protected by Waratek

Waratek has a rule that blocks attacks on this vulnerability.

  • Protection full XXE
  • Action available security rule
  • Review automated Inferred
  • Record active
Decided by A vulnerability class already blocked by an ARMR security rule
Finding Protected by Waratek's ARMR xxe security rule, which blocks this class of attack at the JVM level without a rule written for this CVE specifically. The CVE's weakness is CWE-611: XML External Entity Reference.
Candidate fix https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b : a commit: the change itself

How to mitigate CVE-2026-56817

Upgrade Netty to a release that fixes it: 4.2.16.Final or 4.1.136.Final. Until you can, Waratek RASP blocks exploitation with its XXE rule. It runs inside the Java application, with no code changes.

Waratek RASP Runtime protection for Java applications

CVSS

8.3 HIGH v4.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X 2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

VersionScoreBandVectorAssignerType
CVSS 4.0 8.3 HIGH CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X security-advisories@github.com Secondary published
CVSS 3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H NVD Primary

Affected software and releases

Oracle advisories

AdvisoryTypeQuarterProducts Oracle names in its risk matrix
Oracle Critical Patch Update October 2026 ↗ CPU 2026-Q4 Oracle Communications / Core (Netty) (6.1.1-7.0.0)

Oracle components and versions

FamilyComponentVersions, as Oracle lists themRead as
Oracle Communications Core (Netty) 6.1.1-7.0.0

Maven packages

Affected and fixed versions, from OSV.dev
PackageIntroducedFixedLast affected
io.netty:netty-codec-xml 4.2.0.Final 4.2.16.Final unbounded
io.netty:netty-codec-xml 4.1.0.Final 4.1.136.Final unbounded

Products and versions

2 products, 4 version entries
SourceVendorProductSchemeAffected versions
osv io.netty netty-codec-xml generic ≥ 4.1.0 and < 4.1.136 · ≥ 4.2.0 and < 4.2.16
nvd netty netty generic ≥ 4.1.0 and < 4.1.136 · ≥ 4.2.0 and < 4.2.16

References

URLTags
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b commit
https://github.com/netty/netty/security/advisories/GHSA-4qhr-g3c6-fcfx WEB
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6 WEB
https://github.com/netty/netty PACKAGE
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final WEB
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final WEB

Timeline

Published2026-07-21By the CVE Program.
NVD record modified2026-07-30NVD's own last-modified date for this record.