CVE-2026-56817
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
Netty versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final have a vulnerability in XmlDecoder where delivering XML with a DOCTYPE declaration to an AsyncXMLInputFactory without security configuration can activate DTD and entity handling, creating XML External Entity (XXE) risk.
Risk Assessment
An attacker can exploit XML External Entity to read files on the server or perform SSRF attacks, potentially leading to data leakage or further compromise.
Recommendation
Update Netty to version 4.1.136.Final or 4.2.16.Final.
Original NVD description (English source)
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.