Horizon Alert
Summary of the vulnerability and why it matters
A critical vulnerability in the FrontMCP framework allows unauthenticated attackers to execute arbitrary code on the server. This could expose sensitive information such as API secrets and credentials. The issue arises from how the framework handles sandboxed code execution and Zod schema instances, allowing a script to bypass security measures and gain remote code execution.
- Code execution vulnerability in a server framework.
- Potential exposure of sensitive server secrets.
- Confirm relevance and scope of this framework.
Attack Path
How an attacker could exploit the issue
An attacker can exploit this vulnerability by interacting with the FrontMCP framework, which by default allows unauthenticated access. By sending a crafted request to the `codecall:execute` tool, an attacker can manipulate the framework to expose Zod schema instances. This allows the attacker to access the `_zod.constr.constructor` property, ultimately leading to the execution of arbitrary code on the server. The vulnerability can be triggered by a single tool call, and in default configurations, this can be achieved without any authentication, potentially exposing sensitive server information.
- Entry condition: Public server mode, unauthenticated access.
- Trigger point: Call the `codecall:execute` tool.
- Resulting risk: Arbitrary code execution, server secrets exposed.
Live Threat
Current exploitation, exposure, and threat context
The FrontMCP framework's sandboxed code execution feature can be exploited to gain remote code execution on the server. This occurs when a script accesses live Zod schema instances through the `getTool()` function, allowing it to reach the host's `Function` constructor and execute arbitrary code. This could expose sensitive server-side information such as OAuth client secrets, JWT secrets, session keys, database credentials, and cloud instance metadata.
- Sensitive server secrets and credentials.
- Arbitrary code execution via tool access.
- Complete server compromise and data theft.
Operational Fix
Recommended remediation, mitigation, and detection steps
The Platform or Application Development team is likely responsible for managing the FrontMCP framework. The first practical step is to inventory all instances of this framework, determine their accessibility and business criticality, and identify the accountable owner for each. Subsequently, a remediation plan can be developed based on the assessed risk.
- Identify accountable platform owners.
- Verify exposure and critical systems.
- Plan and coordinate secure updates.
