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CVE-2026-56817

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

CRITICAL
9.8
CVSS Score
Published: July 21, 2026 at 10:06 PM UTC
Updated: July 30, 2026 at 06:22 PM UTC
1 product affected across 1 vendorNetty

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Severity
CRITICAL9.8
Exploit prediction
EPSS 0.7%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Netty· Nettymaven
95%
v < 4.1.136.Finalv < 4.2.16.Final4.1.0 ≤ v < 4.1.1364.2.0 ≤ v < 4.2.16
Affected range stops below 4.1.136, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.1.136.Final, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.2.16, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.2.16.Final, so it looks safe — our inference, not a vendor statement

References (5)

x_refsource_CONFIRMVendor Advisory
Source: cverecord
https://github.com/netty/netty/security/advisories/GHSA-4qhr-g3c6-fcfx
x_refsource_MISCPatch
Source: cverecord
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b
x_refsource_MISCPatch
Source: cverecord
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

9.8CRITICAL[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-611

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