---
id: "CVE-2026-32284"
kind: "vulnerability"
aliases: ["CVE-2026-32284", "GHSA-h9q6-hc68-35rp", "GO-2026-4513"]
title: "Denial of service in github.com/shamaton/msgpack"
severity: "high"
cvss: 7.5
epss: 0.00722
exploited: false
status: "open"
category: "package"
products: [{"name": "github.com/shamaton/msgpack", "fixed": [], "affected": "all versions", "ecosystem": "go"}, {"name": "github.com/shamaton/msgpack/v2", "fixed": ["2.4.1"], "affected": "< 2.4.1", "ecosystem": "go"}, {"name": "github.com/shamaton/msgpack/v3", "fixed": ["3.1.1"], "affected": "< 3.1.1", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["go", "msgpack", "package", "shamaton/msgpack"]
not_affected_if: ["no-untrusted-msgpack-input", "not-using-shamaton-msgpack"]
published_at: "2026-03-16T20:27:23+00:00"
first_seen_at: "2026-10-23T19:13:08+00:00"
updated_at: "2026-10-23T21:45:43+00:00"
sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-4513", "first_seen_at": "2026-10-23T19:13:08+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-32284", "first_seen_at": "2026-10-23T19:13:43+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-32284", "first_seen_at": "2026-10-23T19:35:23+00:00"}]
---

# Denial of service in github.com/shamaton/msgpack

The shamaton/msgpack Go library's decoder does not check buffer length for truncated fixext data, so a crafted msgpack input causes an out-of-bounds read and a runtime panic. An attacker who can send msgpack input to the service can crash the process, a denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- go:github.com/shamaton/msgpack affected all versions fixed ?
- go:github.com/shamaton/msgpack/v2 affected < 2.4.1 fixed 2.4.1
- go:github.com/shamaton/msgpack/v3 affected < 3.1.1 fixed 3.1.1

## How to check

Run govulncheck ./... in the Go module and look for GO-2026-4513; or check go.mod for github.com/shamaton/msgpack, msgpack/v2 below 2.4.1, or msgpack/v3 below 3.1.1.

## Fix

Upgrade github.com/shamaton/msgpack/v2 to 2.4.1 or github.com/shamaton/msgpack/v3 to 3.1.1, then rebuild.
The unversioned github.com/shamaton/msgpack has no listed fix; the sources do not say which version to use.

## Timeline

- 2026-10-23T19:13:08+00:00 govuln https://pkg.go.dev/vuln/GO-2026-4513
- 2026-10-23T19:13:43+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-32284
- 2026-10-23T19:35:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-32284

## From the sources

The msgpack decoder fails to properly validate the input buffer length when processing truncated fixext data (format codes 0xd4-0xd8). This can lead to an out-of-bounds read and a runtime panic, allowing a denial of service attack.

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