# CVE-2026-10566: FoundationAgents MetaGPT schema.py Message.check_instruct_content deserialization

> Attackers can execute arbitrary code via unsafe deserialization in MetaGPT's message handling, requiring local access.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jun 2026
- **Updated:** 2 Jun 2026
- **Also known as:** GHSA-3c3g-7hwg-9qmr, PYSEC-2026-2637

## What is CVE-2026-10566?

CVE-2026-10566 is a medium-severity unsafe deserialization vulnerability in FoundationAgents MetaGPT, published on 2 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A weakness has been identified in FoundationAgents MetaGPT up to 0.8.2. This affects the function Message.check_instruct_content of the file metagpt/schema.py. Executing a manipulation of the argument mapping can lead to deserialization. The attack is restricted to local execution. The exploit has been made available to the public and could be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.

Weakness: CWE-502 (Deserialization of Untrusted Data), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-10566?

3 open source packages ship an affected version, including metagpt.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `metagpt` | PyPI | All versions to 0.8.2 | None |
| `metagpt` | PyPI | All versions to 0.8.2 | None |
| `metagpt` | PyPI | All versions to 0.8.2 | None |

## How do I fix CVE-2026-10566?

No fix has been published for CVE-2026-10566 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-10566 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10566 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-10566 and fix it if it is affected.

What it is: CVE-2026-10566 is a medium-severity unsafe deserialization vulnerability in FoundationAgents MetaGPT, published on 2 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10566 exists.

Affected packages and fixed versions:
- metagpt (PyPI): affected all versions up to 0.8.2; no fix listed
- metagpt (PyPI): affected all versions up to 0.8.2; no fix listed
- metagpt (PyPI): affected all versions up to 0.8.2; no fix listed

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-2026-10566/ (Markdown: https://insights.sbomify.com/CVE-2026-10566/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10566
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10566
- OSV: https://osv.dev/vulnerability/CVE-2026-10566

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-10566/
Summaries are generated and may contain mistakes; the official description above is the record.