# CVE-2026-55786: Flyto2 Core: Unauthenticated Command Execution via HTTP MCP `execute_module`

> Unauthenticated attackers can execute arbitrary OS commands via the HTTP MCP endpoint in Flyto2 Core, leading to potential host compromise.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** GHSA-h9f9-h6gm-wc85, PYSEC-2026-2482

## What is CVE-2026-55786?

CVE-2026-55786 is a high-severity command injection vulnerability in flytohub flyto-core, published on 14 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Flyto2 Core is an execution kernel for automation and AI-agent workflows. From 2.26.2 until 2.26.4, the HTTP MCP POST /mcp route accepts unauthenticated JSON-RPC tools/call requests and forwards execute_module arguments to the module registry without the require_auth dependency used by the REST execution routes. An unauthenticated caller can select sandbox.execute_shell and supply its command parameter, which reaches asyncio.create_subprocess_shell with the privileges of the flyto-core server process. The endpoint is reachable locally under the default loopback binding and becomes network reachable when an operator binds the server to a non-loopback interface, allowing arbitrary OS command execution and potential full host compromise. This issue is fixed in version 2.26.4.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command), CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-55786?

3 open source packages ship an affected version, including flyto-core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `flyto-core` | PyPI | From 2.26.2 | 2.26.4 |
| `flyto-core` | PyPI | From 2.26.2 | 2.26.4 |
| `flyto-core` | PyPI | From 2.26.2 | 2.26.4 |

## How do I fix CVE-2026-55786?

Upgrade flyto-core to 2.26.4 or later.

## Is CVE-2026-55786 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55786 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55786 and fix it if it is affected.

What it is: CVE-2026-55786 is a high-severity command injection vulnerability in flytohub flyto-core, published on 14 Oct 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-2026-55786 exists.

Affected packages and fixed versions:
- flyto-core (PyPI): affected from 2.26.2; fixed in 2.26.4
- flyto-core (PyPI): affected from 2.26.2; fixed in 2.26.4
- flyto-core (PyPI): affected from 2.26.2; fixed in 2.26.4

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-2026-55786/ (Markdown: https://insights.sbomify.com/CVE-2026-55786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55786
- OSV: https://osv.dev/vulnerability/CVE-2026-55786

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55786/
Summaries are generated and may contain mistakes; the official description above is the record.