Netty: XML External Entity (XXE) injection via unconfigured XML factory when DTD and entity processing are enabled

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-56817
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-21 23:17:52 UTC
Updated2026-07-22 20:35:40 UTC
DescriptionNetty 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.

Risk And Classification

Primary CVSS: v4.0 8.3 HIGH from [email protected]

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

EPSS: 0.005550000 probability, percentile 0.428890000 (date 2026-07-22)

Problem Types: CWE-611 | CWE-611 CWE-611: Improper Restriction of XML External Entity Reference

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary8.3HIGHCVSS: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/C...
4.0CNADECLARED8.3HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
None
Availability
Low
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Netty Netty affected >= 4.2.0.Final, < 4.2.16.Final Not specified
CNA Netty Netty affected >= 4.1.0.Final, < 4.1.136.Final Not specified

References

ReferenceSourceLinkTags
github.com/netty/netty/releases/tag/netty-4.1.136.Final [email protected] github.com
github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b [email protected] github.com
github.com/netty/netty/releases/tag/netty-4.2.16.Final [email protected] github.com
github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6 [email protected] github.com
github.com/netty/netty/security/advisories/GHSA-4qhr-g3c6-fcfx [email protected] github.com
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