CVE-2026-55376 heym Python Tool Sandbox Escape
Authenticated users can bypass the Python tool sandbox to execute arbitrary code on the backend server.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55376?
CVE-2026-55376 is a high-severity code injection vulnerability in heymrun heym, published on 13 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-55376?
How do I fix CVE-2026-55376?
No fix has been published for CVE-2026-55376 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-55376 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55376 exists.
Sources
Also known as GHSA-wcgw-9hfw-f6f2.