RCE in Heymrun Heym
CVE-2026-55376
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.
Vulnerability class: Command Injection (OS Command Injection)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Heymrun Heym — versions < 0.0.40
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-55376?
- CVE-2026-55376 is a high-severity vulnerability in Heymrun Heym, classified under OS Command Injection. CVSS score: 8.8/10. Published 2026-10-13.
- How severe is CVE-2026-55376?
- High severity. CVSS v3 base score is 8.8 out of 10.