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CVE-2026-56817

9.8 · CRITICAL

Netty is a network application framework for development of protocol servers and clients.

Published Jul 21, 2026CWE-611EPSS 0.69%

Overview

CVE-2026-56817 is a critical-severity vulnerability. It was published on July 21, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003bGitHubgithub.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6GitHubgithub.com/netty/netty/releases/tag/netty-4.1.136.FinalGitHubgithub.com/netty/netty/releases/tag/netty-4.2.16.FinalGitHubgithub.com/netty/netty/security/advisories/GHSA-4qhr-g3c6-fcfx

How CyberStrike helps

Frequently asked questions

What is CVE-2026-56817?

CVE-2026-56817 is a critical-severity vulnerability. It was published on July 21, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-56817?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-56817?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-56817?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-56817 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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