CVE-2026-67531: Code Injection

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.

Is your site exposed to CVE-2026-67531?

Run a free security scan — no signup, results in seconds.

Weakness Type (CWE)

CWE-94 CWE-94

References

Other References

https://github.com/agentfront/frontmcp/commit/209cddd19a8d4db0777f725b527818da7df6f67f https://github.com/agentfront/frontmcp/security/advisories/GHSA-mp29-fxh8-92px

Frequently Asked Questions

What is CVE-2026-67531? +

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.

How do I check if I'm vulnerable to CVE-2026-67531? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-22136

Tabby (formerly Terminus) is a highly configurable terminal emulator. Prior to 1.0.217 , Tabby enables several high-risk Electron Fuses, including …

CVE-2025-24482

A Local Code Injection Vulnerability exists in the product and version listed above. The vulnerability is due to incorrect default …

CVE-2026-59859

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.32.4, Kiota's PHP generator embedded OpenAPI description, default fields, …

CVE-2026-59865

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.32.5, `kiota info` read x-ms-kiota-info.languagesInformation.<language>.dependencyInstallCommand plus dependency name and …

CVE-2026-42890

Actual is an open-source personal finance application. In the macOS desktop application version 25.x (built on Electron 39.2.7), the ELECTRON_RUN_AS_NODE …

CVE-2025-24959

zx is a tool for writing better scripts. An attacker with control over environment variable values can inject unintended environment …

CVE-2026-67531