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CVE-2026-56817— Netty: XML External Entity (XXE) injection via unconfigured XML factory when DTD and entity processing are enabled

Quick assessment

Affected
netty netty
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Netty是Netty团队开源的一款非阻塞I/O客户端-服务器框架,它主要用于开发Java网络应用程序,如协议服务器和客户端等。 Netty 4.2.0.Final至4.2.15.Final版本和4.1.0.Final至4.1.135.Final版本存在输入验证错误漏洞，该漏洞源于发送包含DOCTYPE声明的XML到未配置安全配置的AsyncXMLInputFactory，可能造成XML外部实体风险。

AI Predicted 5.3 Difficulty: Easy EPSS 0.69% · P51

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
netty netty >= 4.2.0.Final, < 4.2.16.Final affected
>= 4.1.0.Final, < 4.1.136.Final affected
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I. Basic Information for CVE-2026-56817

Vulnerability Information
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Vulnerability Title
Netty: XML External Entity (XXE) injection via unconfigured XML factory when DTD and entity processing are enabled
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
XML外部实体引用的不恰当限制(XXE)
Source: CVE Program / CVE List V5
Vulnerability Title
Netty 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Netty是Netty团队开源的一款非阻塞I/O客户端-服务器框架,它主要用于开发Java网络应用程序,如协议服务器和客户端等。 Netty 4.2.0.Final至4.2.15.Final版本和4.1.0.Final至4.1.135.Final版本存在输入验证错误漏洞，该漏洞源于发送包含DOCTYPE声明的XML到未配置安全配置的AsyncXMLInputFactory，可能造成XML外部实体风险。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
netty netty >= 4.2.0.Final, < 4.2.16.Final -

II. Public POCs for CVE-2026-56817

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III. Intelligence Information for CVE-2026-56817

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Vendor Advisories for CVE-2026-56817 (1)

Vendor Pages for CVE-2026-56817 (2)

Same Patch Batch · netty · 2026-07-21 · 7 CVEs total

CVE-2026-55851 8.7 HIGH Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbo
CVE-2026-56819 7.5 HIGH Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is
CVE-2026-56816 7.5 HIGH Netty: Memory Exhaustion via HTTP/3 Reserved Frame Types
CVE-2026-56820 7.4 HIGH Netty: Missing CertificateID Validation in OCSP Response Allows Replay Attacks
CVE-2026-56746 6.5 MEDIUM Netty has a Security Control Bypass via CORS Short-Circuit Failure
CVE-2026-56745 Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaust

IV. Related Vulnerabilities

Same product: netty
Same vendor: netty
Same weakness: CWE-611

V. Comments for CVE-2026-56817

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