# CVE-2026-107302: msgpack5: Truncated map32 headers throw an unexpected error

> A truncated map32 header in msgpack5 causes an unexpected RangeError, potentially terminating requests or workers in applications expecting incomplete buffer errors.

- **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:** 8 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106845, GHSA-8f34-f56x-9xph

## What is CVE-2026-107302?

CVE-2026-107302 is a high-severity denial of service vulnerability in mcollina msgpack5, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the decoder reads the four-byte length of a map32 value before validating that the complete five-byte header is available. A truncated map32 header therefore causes a checked out-of-bounds buffer read and throws RangeError instead of IncompleteBufferError, which can unexpectedly terminate a request, stream, or worker in applications that wait for additional bytes after IncompleteBufferError. There is no adjacent-memory disclosure because the buffer implementation checks bounds. This issue is fixed in version 6.1.0.

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

## Which versions are affected by CVE-2026-107302?

2 open source packages ship an affected version, including msgpack5.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `msgpack5` | npm | From 4.1.0 | 6.1.0 |
| `msgpack5` | npm | From 4.1.0 | 6.1.0 |

## How do I fix CVE-2026-107302?

Upgrade msgpack5 to 6.1.0 or later.

## Is CVE-2026-107302 being exploited?

There is no known exploitation of CVE-2026-107302 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-107302 and fix it if it is affected.

What it is: CVE-2026-107302 is a high-severity denial of service vulnerability in mcollina msgpack5, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-107302 in the wild and no public exploit code.

Affected packages and fixed versions:
- msgpack5 (npm): affected from 4.1.0; fixed in 6.1.0
- msgpack5 (npm): affected from 4.1.0; fixed in 6.1.0

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-2026-107302/ (Markdown: https://insights.sbomify.com/CVE-2026-107302/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-107302
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-107302
- OSV: https://osv.dev/vulnerability/CVE-2026-107302

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-107302/
Summaries are generated and may contain mistakes; the official description above is the record.