SEPTEMBER 5, 2026
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Case File

CVE-2026-56817

CRITICAL · CVSS 9.8 EPSS 0.37% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-07-21 · Last synced 2026-08-20

CyberRota Analysis

AI-Generated

Netty versions 4.2.0.Final to 4.2.15.Final and 4.1.0.Final to 4.1.135.Final are vulnerable to XML external entity (XXE) attacks due to improper handling of `DOCTYPE` declarations in the `XmlDecoder` when used with an insecure `AsyncXMLInputFactory`. This vulnerability can lead to unauthorized access to sensitive data and potentially remote code execution, making it critical for developers and organizations utilizing affected Netty versions to upgrade to 4.1.136.Final or 4.2.16.Final immediately. Prioritization is essential for those managing network applications built on this framework to mitigate the risk of exploitation.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

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CVE
CVE-2026-56817
Severity
CRITICAL
CVSS
9.8
EPSS
0.37%

Original NVD 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.

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