Vulnerability Description
FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). Prior to 1.5.7, the sandboxed codecall:execute tool exposes live host Zod schema instances to the script via getTool(), and because Zod v4 defines _zod as a non-configurable, non-writable own property, the ECMAScript Proxy invariants force the security membrane to hand back the raw host object, letting a script reach _zod.constr.constructor (the host Function constructor) and execute arbitrary code in the server process. A single tools/call is sufficient to escape the sandbox and achieve remote code execution as the server user, exposing everything the process holds such as OAuth client secrets, JWT_SECRET, session keys, database credentials, and cloud instance metadata. Because the framework's DEFAULT_AUTH_OPTIONS is public mode, an unconfigured server serves this to unauthenticated callers, and on authenticated servers an indirect prompt injection in tool output or fetched content can trigger it without a human attackerThis issue is fixed in version 1.5.7.
Related Weaknesses (CWE)
References
- https://github.com/agentfront/frontmcp/commit/209cddd19a8d4db0777f725b527818da7d
- https://github.com/agentfront/frontmcp/security/advisories/GHSA-mp29-fxh8-92px
- https://github.com/agentfront/frontmcp/security/advisories/GHSA-mp29-fxh8-92px
FAQ
What is CVE-2026-67531?
CVE-2026-67531 is a documented vulnerability. FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). Prior to 1.5.7, the sandboxed codecall:execute tool exposes live host Zod schema instances to the script via getTool(), a...
How severe is CVE-2026-67531?
CVSS scoring is not yet available for CVE-2026-67531. Check NVD for updates.
Is there a patch for CVE-2026-67531?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.