SEPTEMBER 19, 2026
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Case File

CVE-2026-59921

MEDIUM · CVSS 5.7 EPSS 0.25% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-07-28 · Last synced 2026-08-27

CyberRota Analysis

AI-Generated

The vulnerability affects the HttpPostRequestEncoder in Netty, allowing attackers to inject arbitrary MIME headers into multipart HTTP request bodies by exploiting unsanitized CRLF characters in user-supplied filenames. This could lead to potential header injection attacks, impacting the integrity and confidentiality of data transmitted. Organizations using affected versions of Netty should prioritize upgrading to versions 4.1.136.Final or 4.2.16.Final to mitigate this risk.

Public Exploit Signal

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

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-59921
Severity
MEDIUM
CVSS
5.7
EPSS
0.25%

Original NVD Description

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.

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