CVE-2026-67546
Heym: Command execution via POST /api/mcp/fetch-tools stdio transport: supplied command is spawned before MCP validation
Description
Heym builds and runs agentic systems and business-process automations on self-hosted infrastructure. Prior to version 0.0.75, the same POST /api/mcp/fetch-tools endpoint (any authenticated user, lowest role) also accepts the stdio transport, which spawns the attacker-supplied command with attacker-supplied args and an environment merged over os.environ. The process executes on the shared backend host before MCP protocol validation fails — so side effects fire regardless of whether the command speaks MCP. This is a distinct weakness class and exploit primitive from the SSRF (Advisory 2) on the same endpoint, and needs a different fix (role gating / opt-in trust boundary rather than egress controls). This issue has been patched in version 0.0.75.
INFO
Published Date :
Nov. 11, 2026, 9:41 p.m.
Last Modified :
Nov. 11, 2026, 9:41 p.m.
Remotely Exploit :
Yes !
Source :
GitHub_M
Affected Products
The following products are affected by CVE-2026-67546
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update Heym to version 0.0.75 or later.
- Apply role gating and opt-in trust boundary configurations.
- Review and restrict access to the fetch-tools endpoint.
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CVE-2026-67546 vulnerability anywhere in the article.