### [CVE-2021-21409](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21409)
![](https://img.shields.io/static/v1?label=Product&message=netty&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=%3C%204.1.61.Final%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=CWE-444%20Inconsistent%20Interpretation%20of%20HTTP%20Requests%20('HTTP%20Request%20Smuggling')&color=brightgreen)

### Description

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty (io.netty:netty-codec-http2) before version 4.1.61.Final there is a vulnerability that enables request smuggling. The content-length header is not correctly validated if the request only uses a single Http2HeaderFrame with the endStream set to to true. This could lead to request smuggling if the request is proxied to a remote peer and translated to HTTP/1.1. This is a followup of GHSA-wm47-8v5p-wjpj/CVE-2021-21295 which did miss to fix this one case. This was fixed as part of 4.1.61.Final.

### POC

#### Reference
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://www.oracle.com/security-alerts/cpuoct2021.html

#### Github
- https://github.com/cezapata/appconfiguration-sample
- https://github.com/n0-traces/cve_monitor