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

> A denial of service vulnerability in the Go msgpack library allows attackers to cause a runtime panic via truncated fixext data.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Mar 2026
- **Updated:** 7 Oct 2026
- **Also known as:** GHSA-h9q6-hc68-35rp, GO-2026-4513

## What is CVE-2026-32284?

CVE-2026-32284 is a high-severity denial of service vulnerability in github.com/shamaton/msgpack, published on 26 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-32284?

7 open source packages ship an affected version, including github.com/shamaton/msgpack/v2, github.com/shamaton/msgpack and github.com/shamaton/msgpack/v3. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/shamaton/msgpack/v2` | Go | All versions to 2.4.0 | None |
| `github.com/shamaton/msgpack/v2` | Go | All versions to 2.4.0 | None |
| `github.com/shamaton/msgpack/v2` | Go | All versions | 2.4.1 |
| `github.com/shamaton/msgpack` | Go | All versions | None |
| `github.com/shamaton/msgpack/v3` | Go | All versions to 3.1.0 | None |
| `github.com/shamaton/msgpack/v3` | Go | All versions to 3.1.0 | None |
| `github.com/shamaton/msgpack/v3` | Go | All versions | 3.1.1 |

Products: Shamaton Msgpack.

## How do I fix CVE-2026-32284?

Upgrade github.com/shamaton/msgpack/v2 to 2.4.1 or later.

## Is CVE-2026-32284 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32284 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-32284 and fix it if it is affected.

What it is: CVE-2026-32284 is a high-severity denial of service vulnerability in github.com/shamaton/msgpack, published on 26 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32284 exists.

Affected packages and fixed versions:
- github.com/shamaton/msgpack/v2 (Go): affected all versions up to 2.4.0; no fix listed
- github.com/shamaton/msgpack/v2 (Go): affected all versions up to 2.4.0; no fix listed
- github.com/shamaton/msgpack/v2 (Go): affected all versions; fixed in 2.4.1
- github.com/shamaton/msgpack (Go): affected all versions; no fix listed
- github.com/shamaton/msgpack/v3 (Go): affected all versions up to 3.1.0; no fix listed
- github.com/shamaton/msgpack/v3 (Go): affected all versions up to 3.1.0; no fix listed
- github.com/shamaton/msgpack/v3 (Go): affected all versions; fixed in 3.1.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-32284/ (Markdown: https://insights.sbomify.com/CVE-2026-32284/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-32284
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32284
- OSV: https://osv.dev/vulnerability/CVE-2026-32284

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-32284/
Summaries are generated and may contain mistakes; the official description above is the record.