Withdrawn by the publisher.

Affected: CleanStart: keycloak

Multiple security vulnerabilities affect the keycloak package. These issues are resolved in later releases. See references for individual vulnerability details.

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, 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. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

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 |

---

## 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.

---

## 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()…

netty-4.1.133-1.1 on GA media

netty: io.netty/netty-handler-proxy: Netty: HTTP Header Injection via HttpProxyHandler Disabled Validation netty: Netty: High integrity impact due to improper DNS domain name constraint enforcement netty: io.netty/netty-codec-http: Netty: HTTP Request Smuggling due to improper handling of conflicting HTTP/1.0 headers netty: io.netty/netty-codec-http: Netty: Incorrect HTTP response parsing leads to data confusion netty: io.netty/netty-codec-http: io.netty/netty-codec-http2: Netty: Denial of Service via unbounded memory allocation in HTTP content decompression

Affected: Ubuntu:Pro:14.04:LTS: netty, Ubuntu:Pro:16.04:LTS: netty, Ubuntu:Pro:18.04:LTS: netty, Ubuntu:Pro:20.04:LTS: netty, Ubuntu:Pro:22.04:LTS: netty, Ubuntu:Pro:24.04:LTS: netty, Ubuntu:25.10: netty, Ubuntu:Pro:26.04:LTS: netty

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, 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. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Netty ausnutzen, um Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand zu verursachen.