CVE-2025-58056

Netty is an asynchronous event-driven network application framework for development of maintainable high performance protocol servers and clients. In versions 4.1.124.Final, and 4.2.0.Alpha3 through 4.2.4.Final, Netty incorrectly accepts standalone newline characters (LF) as a chunk-size line terminator, regardless of a preceding carriage return (CR), instead of requiring CRLF per HTTP/1.1 standards. When combined with reverse proxies that parse LF differently (treating it as part of the chunk extension), attackers can craft requests that the proxy sees as one request but Netty processes as two, enabling request smuggling attacks. This is fixed in versions 4.1.125.Final and 4.2.5.Final.

A client might overload the server by issue frequent RST frames. This can cause a massive amount of load on the remote system and so cause a DDOS attack.

Impact

This is a DDOS attack, any http2 server is affected and so you should update as soon as possible.

Patches

This is patched in version 4.1.100.Final.

Workarounds

A user can limit the amount of RST frames that are accepted per connection over a timeframe manually using either an own Http2FrameListener implementation or an ChannelInboundHandler implementation (depending which http2 API is used).

References

• https://www.cve.org/CVERecord?id=CVE-2023-44487
• https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/
• https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-above-398-million-rps/

Red Hat Lightwell has released io.netty:netty-codec-http 4.1.100.Final-rhlw-00001 with backported fixes for CVE-2024-29025, CVE-2025-58056, CVE-2025-67735, CVE-2026-33870, CVE-2026-41417, CVE-2026-42580, CVE-2026-42581, CVE-2026-42584, CVE-2026-42585, CVE-2026-42587, CVE-2026-50020, CVE-2026-55831, CVE-2026-55833, CVE-2026-56745, CVE-2026-56746, CVE-2026-59898, CVE-2026-59899, CVE-2026-59903, and CVE-2026-59921.

CVE-2024-29025: Netty HttpPostRequestDecoder can OOM

CVE-2025-58056: Netty is vulnerable to request smuggling due to incorrect parsing of chunk extensions

CVE-2025-67735: Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder

CVE-2026-33870: Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing

CVE-2026-41417: Netty vulnerable to HTTP request smuggling and RTSP request injection via DefaultHttpRequest.setUri()

CVE-2026-42580: Netty: HTTP Request Smuggling due to incorrect chunk size parsing

CVE-2026-42581: Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization

CVE-2026-42584: Netty: HttpClientCodec response desynchronization

CVE-2026-42585: Netty: HTTP Request Smuggling due to malformed Transfer-Encoding

CVE-2026-42587: Netty: HttpContentDecompressor maxAllocation bypass via Content-Encoding: br/zstd/snappy enables decompression bomb DoS

CVE-2026-50020: Netty's HttpObjectDecoder skips arbitrary initial control characters when only initial CRLF characters are permitted

CVE-2026-55831: Netty SPDY SETTINGS frame count materializes unbounded settings map

CVE-2026-55833: Netty SPDY zlib header block continues decoded expansion after maxHeaderSize truncation

CVE-2026-56745: Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion

CVE-2026-56746: Netty has a Security Control Bypass via CORS Short-Circuit Failure

CVE-2026-59898: Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation

CVE-2026-59899: Netty HttpContentEncoder: Unbounded Per-Connection Queue Growth via HTTP/1.1 Pipelining Leads to Denial of Service

CVE-2026-59903: Netty: Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite

CVE-2026-59921: Netty: CRLF Injection via Multipart Filename in Netty HttpPostRequestEncoder

This patched artifact is a drop-in replacement for io.netty:netty-codec-http 4.1.100.Final from Maven Central.

Root has patched GHSA-xpw8-rcwv-8f8p in the io.root.io.netty:netty-codec-http2 package for Root:Maven. Multiple fixed versions available.

Netty is an asynchronous event-driven network application framework for development of maintainable high performance protocol servers and clients. In versions 4.1.124.Final, and 4.2.0.Alpha3 through 4.2.4.Final, Netty incorrectly accepts standalone newline characters (LF) as a chunk-size line terminator, regardless of a preceding carriage return (CR), instead of requiring CRLF per HTTP/1.1 standards. When combined with reverse proxies that parse LF differently (treating it as part of the chunk extension), attackers can craft requests that the proxy sees as one request but Netty processes as two, enabling request smuggling attacks. This is fixed in versions 4.1.125.Final and 4.2.5.Final.

TuxCare rebuilt 40 io.netty packages to address 16 CVEs. Fixed in 4.1.52.Final-tuxcare.1.

TuxCare rebuilt 46 io.netty packages to address 9 CVEs. Fixed in 4.1.75.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 12 CVEs. Fixed in 4.1.93.Final-tuxcare.1.

TuxCare rebuilt 3 io.netty packages to address 4 CVEs. Fixed in 4.1.115.Final-tuxcare.4.

TuxCare rebuilt io.netty:netty-codec-http to address 1 CVE. Fixed in 4.1.112.Final-tuxcare.3.

TuxCare rebuilt io.netty:netty-codec-http to address 2 CVEs. Fixed in 4.1.92.Final-tuxcare.2.

TuxCare rebuilt 47 io.netty packages to address 59 CVEs. Fixed in 4.1.122.Final-tuxcare.2.

TuxCare rebuilt 47 io.netty packages to address 60 CVEs. Fixed in 4.1.119.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 62 CVEs. Fixed in 4.1.111.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 48 CVEs. Fixed in 4.1.117.Final-tuxcare.3.

TuxCare rebuilt 47 io.netty packages to address 61 CVEs. Fixed in 4.1.108.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 61 CVEs. Fixed in 4.1.107.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 62 CVEs. Fixed in 4.1.94.Final-tuxcare.1.

TuxCare rebuilt 12 io.netty packages to address 28 CVEs. Fixed in 4.1.79.Final-tuxcare.2.

TuxCare rebuilt 11 io.netty packages to address 18 CVEs. Fixed in 4.1.87.Final-tuxcare.1.

TuxCare rebuilt 5 io.netty packages to address 9 CVEs. Fixed in 4.1.48.Final-tuxcare.4.

TuxCare rebuilt io.netty:netty to address 4 CVEs. Fixed in 3.7.0.Final-tuxcare.1.

TuxCare rebuilt 6 io.netty packages to address 13 CVEs. Fixed in 4.1.42.Final-tuxcare.1.

TuxCare rebuilt 14 io.netty packages to address 26 CVEs. Fixed in 4.1.118.Final-tuxcare.1.

TuxCare rebuilt 13 io.netty packages to address 24 CVEs. Fixed in 4.1.114.Final-tuxcare.1.

TuxCare rebuilt io.netty:netty to address 4 CVEs. Fixed in 3.5.13.Final-tuxcare.1.

TuxCare rebuilt io.netty:netty to address 2 CVEs. Fixed in 3.10.6.Final-tuxcare.3.

TuxCare rebuilt 6 io.netty packages to address 11 CVEs. Fixed in 4.1.39.Final-tuxcare.1.

TuxCare rebuilt 4 io.netty packages to address 6 CVEs. Fixed in 4.1.24.Final-tuxcare.1.

TuxCare rebuilt 4 io.netty packages to address 6 CVEs. Fixed in 4.1.29.Final-tuxcare.1.

TuxCare rebuilt 7 io.netty packages to address 10 CVEs. Fixed in 4.1.21.Final-tuxcare.1.

TuxCare rebuilt 3 io.netty packages to address 4 CVEs. Fixed in 4.0.56.Final-tuxcare.1.

TuxCare rebuilt 6 io.netty packages to address 7 CVEs. Fixed in 4.1.31.Final-tuxcare.1.

TuxCare rebuilt 8 io.netty packages to address 11 CVEs. Fixed in 4.1.43.Final-tuxcare.3.

TuxCare rebuilt 6 io.netty packages to address 8 CVEs. Fixed in 4.1.38.Final-tuxcare.1.

TuxCare rebuilt 6 io.netty packages to address 7 CVEs. Fixed in 4.1.23.Final-tuxcare.1.

TuxCare rebuilt 14 io.netty packages to address 16 CVEs. Fixed in 4.2.2.Final-tuxcare.1.

TuxCare rebuilt io.netty:netty to address 4 CVEs. Fixed in 3.6.2.Final-tuxcare.1.

TuxCare rebuilt org.jboss.netty:netty to address 1 CVE. Fixed in 3.2.4.Final-tuxcare.2.

TuxCare rebuilt 13 io.netty packages to address 24 CVEs. Fixed in 4.1.74.Final-tuxcare.1.

TuxCare rebuilt 10 io.netty packages to address 17 CVEs. Fixed in 4.1.49.Final-tuxcare.6.

TuxCare rebuilt 9 io.netty packages to address 13 CVEs. Fixed in 4.1.113.Final-tuxcare.2.

Summary

A flaw in netty's parsing of chunk extensions in HTTP/1.1 messages with chunked encoding can lead to request smuggling issues with some reverse proxies.

Details

When encountering a newline character (LF) while parsing a chunk extension, netty interprets the newline as the end of the chunk-size line regardless of whether a preceding carriage return (CR) was found. This is in violation of the HTTP 1.1 standard which specifies that the chunk extension is terminated by a CRLF sequence (see the RFC).

This is by itself harmless, but consider an intermediary with a similar parsing flaw: while parsing a chunk extension, the intermediary interprets an LF without a preceding CR as simply part of the chunk extension (this is also in violation of the RFC, because whitespace characters are not allowed in chunk extensions). We can use this discrepancy to construct an HTTP request that the intermediary will interpret as one request but netty will interpret as two (all lines ending with CRLF, notice the LFs in the chunk extension):

POST /one HTTP/1.1
Host: localhost:8080
Transfer-Encoding: chunked

48;\nAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\n0

POST /two HTTP/1.1
Host: localhost:8080
Transfer-Encoding: chunked

0

The intermediary will interpret this as a single request. Once forwarded to netty, netty will interpret it as two separate requests. This is a problem, because attackers can then the intermediary, as well as perform standard request smuggling attacks against other live users (see this Portswigger article).

Impact

This is a request smuggling issue which can be exploited for bypassing front-end access control rules as well as corrupting the responses served to other live clients.

The impact is high, but it only affects setups that use a front-end which:

1. Interprets LF characters (without preceding CR) in chunk extensions as part of the chunk extension.
2. Forwards chunk extensions without normalization.

Disclosure

• This vulnerability was disclosed on June 18th, 2025 here: https://w4ke.info/2025/06/18/funky-chunks.html

Discussion

Discussion for this vulnerability can be found here:

• https://github.com/netty/netty/issues/15522
• https://github.com/JLLeitschuh/unCVEed/issues/1

Credit

• Credit to @JeppW for uncovering this vulnerability.
• Credit to @JLLeitschuh at Socket for coordinating the vulnerability disclosure.

These are all security issues fixed in the netty-4.1.126-1.1 package on the GA media of openSUSE Tumbleweed.

This update for netty, netty-tcnative fixes the following issues:

Upgrade to upstream version 4.1.126.

Security issues fixed:

• CVE-2025-58057: decompression codecs allocating a large number of buffers after processing specially crafted input can cause a denial of service (bsc#1249134).
• CVE-2025-58056: incorrect parsing of chunk extensions can lead to request smuggling (bsc#1249116).
• CVE-2025-55163: 'MadeYouReset' denial of serivce attack in the HTTP/2 protocol (bsc#1247991).

Other issues fixed:

• Fixes from version 4.1.126

  • Fix IllegalReferenceCountException on invalid upgrade response.
  • Drop unknown frame on missing stream.
  • Don't try to handle incomplete upgrade request.
  • Update to netty-tcnative 2.0.73Final.

• Fixes from version 4.1.124

  • Fix NPE and AssertionErrors when many tasks are scheduled and cancelled.
  • HTTP2: Http2ConnectionHandler should always use Http2ConnectionEncoder.
  • Epoll: Correctly handle UDP packets with source port of 0.
  • Fix netty-common OSGi Import-Package header.
  • MqttConnectPayload.toString() includes password.

• Fixes from version 4.1.123

  • Fix chunk reuse bug in adaptive allocator.
  • More accurate adaptive memory usage accounting.
  • Introduce size-classes for the adaptive allocator.
  • Reduce magazine proliferation eagerness.
  • Fix concurrent ByteBuffer access issue in AdaptiveByteBuf.getBytes.
  • Fix possible buffer corruption caused by incorrect setCharSequence(...) implementation.
  • AdaptiveByteBuf: Fix AdaptiveByteBuf.maxFastWritableBytes() to take writerIndex() into account.
  • Optimize capacity bumping for adaptive ByteBufs.
  • AbstractDnsRecord: equals() and hashCode() to ignore name field's case.
  • Backport Unsafe guards.
  • Guard recomputed offset access with hasUnsafe.
  • HTTP2: Always produce a RST frame on stream exception.
  • Correct what artifacts included in netty-bom.

• Fixes from version 4.1.122

  • DirContextUtils.addNameServer(...) should just catch Exception internally.
  • Make public API specify explicit maxAllocation to prevent OOM.
  • Fix concurrent ByteBuf write access bug in adaptive allocator.
  • Fix transport-native-kqueue Bundle-SymbolicNames.
  • Fix resolver-dns-native-macos Bundle-SymbolicNames.
  • Always correctly calculate the memory address of the ByteBuf even if sun.misc.Unsafe is not usable.
  • Upgrade lz4 dependencies as the old version did not correctly handle ByteBuffer that have an arrayOffset > 0.
  • Optimize ByteBuf.setCharSequence for adaptive allocator.
  • Kqueue: Fix registration failure when fd is reused.
  • Make JdkZlibEncoder accept Deflater.DEFAULT_COMPRESSION as level.
  • Ensure OpenSsl.availableJavaCipherSuites does not contain null values.
  • Always prefer direct buffers for pooled allocators if not explicit disabled.
  • Update to netty-tcnative 2.0.72.Final.
  • Re-enable sun.misc.Unsafe by default on Java 24+.
  • Kqueue: Delay removal from registration map to fix noisy warnings.

• Fixes from version 4.1.121

  • Epoll.isAvailable() returns false on Ubuntu 20.04/22.04 arch amd64.
  • Fix transport-native-epoll Bundle-SymbolicNames.

• Fixes from version 4.1.120

  • Fix flawed termination condition check in HttpPostRequestEncoder#encodeNextChunkUrlEncoded(int) for current InterfaceHttpData.
  • Exposed decoderEnforceMaxConsecutiveEmptyDataFrames and decoderEnforceMaxRstFramesPerWindow.
  • ThreadExecutorMap must restore old EventExecutor.
  • Make Recycler virtual thread friendly.
  • Disable sun.misc.Unsafe by default on Java 24+.
  • Adaptive: Correctly enforce leak detection when using AdaptiveByteBufAllocator.
  • Add suppressed exception to original cause when calling Future.sync*.
  • Add SETTINGS_ENABLE_CONNECT_PROTOCOL to the default HTTP/2 settings.
  • Correct computation for suboptimal chunk retirement probability.
  • Fix bug in method AdaptivePoolingAllocator.allocateWithoutLock(...).
  • Fix a Bytebuf leak in TcpDnsQueryDecoder.
  • SSL:…