# Netty Lz4FrameDecoder is vulnerable to resource exhaustion

Advisory record · `GHSA-mj4r-2hfc-f8p6`

- **Identifiers:** `GHSA-mj4r-2hfc-f8p6` · `CVE-2026-42583`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-770](https://cwe.mitre.org/data/definitions/770.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 7 May 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 7 May 2026, 00:20 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `io.netty:netty-codec-compression` (Maven): affected `<4.2.13.Final`; fixed in `4.2.13.Final`
- `io.netty:netty-codec` (Maven): affected `<4.1.133.Final`; fixed in `4.1.133.Final`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Netty's netty-codec-compression package, versions before 4.2.13.Final, and netty-codec, versions before 4.1.133.Final, are affected by a resource exhaustion flaw in the Lz4FrameDecoder. A remote peer that sends a small crafted LZ4 frame, around 22 bytes, can force the decoder to allocate up to 32 MB of memory before decompression runs, so many such requests can exhaust memory. Upgrade netty-codec-compression to 4.2.13.Final and netty-codec to 4.1.133.Final. The source gives few details on limits that could mitigate this.

Written 2 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0046, the 40th percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:16 UTC: First seen by agentprime
- 31 Oct 2026, 14:16 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-mj4r-2hfc-f8p6)

## Sources

- [GitHub Advisory Database: GHSA-mj4r-2hfc-f8p6](https://github.com/advisories/GHSA-mj4r-2hfc-f8p6)
- [OSV: GHSA-mj4r-2hfc-f8p6](https://osv.dev/vulnerability/GHSA-mj4r-2hfc-f8p6)
- <https://github.com/netty/netty/security/advisories/GHSA-mj4r-2hfc-f8p6>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-42583>
- <https://github.com/netty/netty>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-mj4r-2hfc-f8p6>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-mj4r-2hfc-f8p6/>. Everything for agents: <https://agentprime.io/llms.txt>.