Affected: Maven: io.netty:netty-codec-http

# NETTY HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization

| Field | Value | |-----------|-------| | Library | `io.netty:netty-codec-http` | | Component | `codec-http` — `HttpObjectDecoder` | | Severity | **HIGH** | | Affects | HEAD, commit `4f3533ae` confirmed |

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## Summary

`HttpObjectDecoder` strips a conflicting `Content-Length` header when a request carries both `Transfer-Encoding: chunked` and `Content-Length`, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving `Content-Length` intact in the forwarded `HttpMessage`. Any downstream proxy or handler that trusts `Content-Length` over `Transfer-Encoding` will disagree on message boundaries, enabling request smuggling.

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## Root Cause

```java // HttpObjectDecoder.java:828-833 if (HttpUtil.isTransferEncodingChunked(message)) { this.chunked = true; if (!contentLengthFields.isEmpty() && message.protocolVersion() == HttpVersion.HTTP_1_1) { handleTransferEncodingChunkedWithContentLength(message); // strips CL — HTTP/1.1 only } return State.READ_CHUNK_SIZE; }

// HttpObjectDecoder.java:870-873 protected void handleTransferEncodingChunkedWithContentLength(HttpMessage message) { message.headers().remove(HttpHeaderNames.CONTENT_LENGTH); contentLength = Long.MIN_VALUE; } ```

The conflict-resolution path is gated on `message.protocolVersion()…