Horizon Alert
Summary of the vulnerability and why it matters
A path traversal vulnerability has been identified in a tool used for constructing API requests, potentially allowing unauthorized access to sensitive information or system functions on the same host. This issue affects how user-provided data is processed when building URLs, enabling an attacker to bypass intended path restrictions. The main concern is confirming relevance and exposure.
- Attackers can bypass security restrictions.
- Confirms potential for unauthorized access.
- Understand potential impact on internal systems.
Attack Path
How an attacker could exploit the issue
An attacker could exploit this vulnerability by sending specially crafted requests to the HTTP tool URL builder. This component is used to construct downstream API requests, and an attacker could provide path parameters containing directory traversal sequences, such as "../". Although some checks are in place, the system relies on URL resolution that normalizes these sequences. This allows an attacker to break out of the intended path and potentially access sensitive information or perform actions on unintended endpoints on the same host, using the toolbox's credentials.
- No authentication or privileges required.
- User-supplied parameters in URL construction.
- Access sensitive data or execute unintended actions.
Live Threat
Current exploitation, exposure, and threat context
This vulnerability could allow an attacker to trick the HTTP tool URL builder into making requests to unintended endpoints on the same host. This is possible when the builder substitutes user-controlled path parameters into a configured tool path and resolves the resulting string as a relative URL. When supported, the attacker could leverage this to bypass path restrictions and access sensitive administrative or secret endpoints, potentially forwarding the toolbox's configured credentials.
- Tool path configuration.
- Directory traversal sequences.
- Unauthorized access to host endpoints.
Operational Fix
Recommended remediation, mitigation, and detection steps
The googleapis/mcp-toolbox library's HTTP tool URL builder is susceptible to path traversal, allowing an attacker to reach unintended endpoints on a target host by manipulating path parameters. This could expose sensitive information or allow unauthorized actions, especially if the toolbox is operating with elevated privileges.
- Ownership: Application owners and platform teams.
- Verify: Reachability and business criticality.
- Action: Plan remediation or mitigate risk.
