---
id: CVE-2026-107299
title: msgpack5 is a msgpack v5 implementation for node.js and the browser
summary: >-
  msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to
  6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as
  incomplete input instead of invalid input. When 0xc1 begins a stream,
  subsequent data…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-228
vendor: msgpack5
product: msgpack5
affected:
  - msgpack5 < 6.1.0
patched:
  - msgpack5 6.1.0
published: '2026-10-08'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T20:48:36.970'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107299'
references:
  - url: >-
      https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314
    label: security-advisories@github.com
  - url: 'https://github.com/mcollina/msgpack5/releases/tag/v6.1.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-26wq-p25c-j6fv'
tags:
  - nvd
  - ghsa
  - npm
  - cve.org
aliases:
  - GHSA-26wq-p25c-j6fv
ecosystem: npm
ingestedAt: '2026-10-08T17:56:11.715Z'
---

## Overview

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-107299)

Affected packages:

- `msgpack5 < 6.1.0`

Patched in:

- `msgpack5 6.1.0`

Source: https://github.com/advisories/GHSA-26wq-p25c-j6fv