CVE-2026-59921

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, HttpPostRequestEncoder constructs multipart HTTP request bodies by directly concatenating user-supplied filenames and field names into Content-Disposition MIME headers without validating or sanitizing CRLF characters (\r\n). Since MIME headers are delimited by CRLF, an attacker who controls the filename can inject arbitrary MIME headers into the multipart body part. The root cause is that neither the encoder nor the FileUpload implementations' setFilename() methods, which only check for null, neutralize CRLF characters before the filename is embedded into the header. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

• CWE-93

• https://github.com/netty/netty/security/advisories/GHSA-gcjf-9mgh-3p7gMitigation, Vendor Advisory
• https://github.com/netty/netty/security/advisories/GHSA-gcjf-9mgh-3p7gMitigation, Vendor Advisory

Published

Jul 28, 2026

Last Modified

Aug 7, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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