Affected: Maven: io.netty:netty-handler-proxy

# Security Vulnerability Report: HTTP Header Injection via HttpProxyHandler Disabled Validation in Netty

## 1. Vulnerability Summary

| Field | Value | |-------|-------| | **Product** | Netty | | **Version** | 4.2.12.Final (and all prior versions) | | **Component** | `io.netty.handler.proxy.HttpProxyHandler` | | **Vulnerability Type** | CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers | | **Impact** | HTTP Header Injection in CONNECT Proxy Requests | | **CVSS 3.1 Score** | **7.5 (High)** | | **CVSS 3.1 Vector** | `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N` | | **Related Advisory** | **GHSA-84h7-rjj3-6jx4** (Incomplete Fix) |

## 2. Affected Components

- `io.netty.handler.proxy.HttpProxyHandler` — `newInitialMessage()` method (line 176) explicitly disables header validation via `withValidation(false)`

## 3. Vulnerability Description

Netty's `HttpProxyHandler` constructs HTTP CONNECT requests with **header validation explicitly disabled**. The `newInitialMessage()` method (line 176) creates headers using `DefaultHttpHeadersFactory.headersFactory().withValidation(false)`, then adds user-provided `outboundHeaders` (line 188-190) without any CRLF validation. This allows an attacker who can influence the outbound headers to inject arbitrary HTTP headers into the CONNECT request sent to the proxy server.

### Root Cause

```java // HttpProxyHandler.java:176-190 protected Object newInitialMessage(ChannelHandlerContext ctx) throws Exception { // ... H…