---
id: CVE-2026-42582
title: 'Netty is an asynchronous, event-driven network application framework'
summary: >-
  Netty is an asynchronous, event-driven network application framework. Prior to
  4.2.13.Final, when decoding header blocks, the non-Huffman branch of
  io.netty.handler.codec.http3.QpackDecoder#decodeHuffmanEncodedLiteral may
  execute new byt…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
  - CWE-789
vendor: netty
product: netty
affected:
  - 'netty >= 4.2.0, < 4.2.13'
patched:
  - netty 4.2.13
published: '2026-05-13'
updated: '2026-07-10'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-42582'
references:
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-2c5c-chwr-9hqw'
    label: security-advisories@github.com
  - url: 'https://github.com/netty/netty/security/advisories/GHSA-2c5c-chwr-9hqw'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00486
epssPercentile: 0.39207
ingestedAt: '2026-07-10T16:05:09.791Z'
---

## Overview

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final, 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]. This vulnerability is fixed in 4.2.13.Final.

## Affected

- `netty >= 4.2.0, < 4.2.13`

## Remediation

Upgrade past the affected range:

- `netty 4.2.13`