Red Hat Netty 1.1 HTTPObjectDecoder HttpObjectDecoder.java request smuggling

Summaryinfo

A vulnerability classified as problematic was found in Red Hat Netty 1.1. The affected element is the function io.netty.handler.codec.http.HttpObjectDecoder.checkChunkExtensions of the file HttpObjectDecoder.java of the component HTTPObjectDecoder. Executing a manipulation can lead to request smuggling. This vulnerability is tracked as CVE-2026-93566. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability classified as problematic was found in Red Hat Netty 1.1. This vulnerability affects the function io.netty.handler.codec.http.HttpObjectDecoder.checkChunkExtensions of the file HttpObjectDecoder.java of the component HTTPObjectDecoder. The manipulation with an unknown input leads to a request smuggling vulnerability. The CWE definition for the vulnerability is CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. As an impact it is known to affect integrity. CVE summarizes:

### 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

The advisory is shared for download at access.redhat.com. This vulnerability was named CVE-2026-93566 since 09/18/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 09/18/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Red Hat

Name

• Netty

Version

• 1.1

License

• open-source

Website

• Vendor: https://www.redhat.com/

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