CVE-2026-67546 · AI agents & MCP
NO FIX YET · SEE WHAT TO DO
Heym's MCP fetch-tools endpoint accepts the stdio transport, which spawns an attacker-supplied command with attacker-supplied arguments and environment on the backend host. Any authenticated user, including the lowest role, can execute code on the shared server before MCP validation fails.
first public Jul 21, 2026 · 1 source
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Teams that self-host Heym on a shared backend host where any authenticated user, including the lowest role, can reach the MCP fetch-tools endpoint. Instances that restrict this endpoint to trusted users or do not run Heym before 0.0.75 are less exposed; the sources do not say more.
Not affected if version-0.0.75-or-later
Who cares heym, mcp, self-hosted
0.0.750.0.75 or laterHeym 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.
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