Summary
A high-severity information disclosure vulnerability in mcp-remote may expose sensitive information through its authorization-server metadata and utility components. The issue becomes risky when a remote party can reach the affected functionality and retrieve data that should remain limited to trusted clients or internal processing.
Affected context
The vulnerability affects mcp-remote releases from 0.1.32 through 0.1.38 and is associated with:
src/lib/authorization-server-metadata.tssrc/lib/utils.ts
Exposure depends on the affected components being reachable through a network-facing workflow and returning information without adequately restricting its visibility or sensitivity.
Exploit preconditions
- Attack surface: Network-accessible mcp-remote functionality involving authorization-server metadata or related utilities
- Required access: A remote connection capable of invoking or reaching the affected behavior; authentication requirements may vary by deployment
- Trigger point: Processing or serving data through the affected TypeScript components
- Why exploitation is possible: Sensitive information may be returned to a remote requester without sufficient access control, filtering, or confidentiality enforcement
Why this happens
The underlying issue is an information exposure weakness in which data handled by authorization metadata or utility logic can become accessible beyond its intended trust boundary.
This maps to CWE-200: Exposure of Sensitive Information to an Unauthorized Actor. The insecure pattern is the propagation or disclosure of internal, credential-related, configuration, or other sensitive data without consistently applying authorization, minimization, and response-scope controls.
Potential impact
- An attacker may obtain sensitive authorization or service metadata
- Exposed information could assist reconnaissance against connected services
- Disclosure may reveal configuration details or identifiers useful for follow-on attacks
- Sensitive data exposure could affect the confidentiality of users, integrations, or backend systems
General mitigation guidance
Mitigation generally focuses on reducing the amount of sensitive information exposed through remote responses and enforcing trust boundaries consistently.
Common defensive patterns include:
- Returning only the minimum metadata required by the client or protocol
- Applying authentication and authorization checks before exposing sensitive responses
- Separating public discovery data from internal configuration and credential material
- Redacting secrets, tokens, private endpoints, and unnecessary identifiers from serialized output
- Using least-privilege service identities and limiting access to connected systems
- Treating all remotely supplied context as untrusted and avoiding implicit disclosure through utility functions
How teams detect issues like this
Organizations can assess for this class of issue through:
- Static analysis and code review of response construction, metadata handling, and utility functions
- Tracing whether sensitive values can flow from configuration or authorization state into network responses
- Reviewing route and middleware policies for missing authentication or authorization checks
- Testing unauthenticated and low-privilege requests for excessive metadata or internal details
- Enforcing policies that prohibit secrets and sensitive configuration values in externally visible responses
Automated review tools may help identify suspicious data flows, but findings should be validated against the deployment's trust boundaries.
