CRLF Injection Affecting io.netty:netty-codec-http package, versions [,4.1.136.Final)[4.2.0.Final,4.2.16.Final)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JAVA-IONETTY-18231070
- published23 Jul 2026
- disclosed22 Jul 2026
- creditUnknown
Introduced: 22 Jul 2026
NewCVE-2026-59921 (opens in a new tab)How to fix?
Upgrade io.netty:netty-codec-http to version 4.1.136.Final, 4.2.16.Final or higher.
Overview
io.netty:netty-codec-http is a network application framework for rapid development of maintainable high performance protocol servers & clients.
Affected versions of this package are vulnerable to CRLF Injection in the HttpPostRequestEncoder. An attacker can inject arbitrary MIME headers and manipulate multipart request bodies by supplying crafted filenames containing CRLF sequences. This can lead to overriding Content-Type headers, injecting malicious scripts, or altering form data processed by downstream services.
Note: This is only exploitable if the application uses the multipart encoder with filenames derived from user-controlled input and does not perform its own CRLF sanitization.