APIFold, a tool that generates MCP server endpoints from OpenAPI/Swagger specs, had a missing authentication check on its webhook endpoint. Specifically, the /webhooks/:serverSlug/:eventName endpoint accepted arbitrary JSON without signature validation due to the absence of a validators map in the createWebhookRouter call. This caused the signature validation code to be skipped unconditionally, allowing unauthenticated clients to inject arbitrary payloads into Redis and the webhook_events PostgreSQL table. This injected data could then be served as trusted state to legitimate clients. The vulnerability was patched in commit 7f19b52280f414f57af2b79a95333d1c8fbeece5.

An unauthenticated attacker who knows a valid server slug can inject arbitrary JSON payloads into the system's Redis cache and PostgreSQL database. These payloads are then treated as trusted data by legitimate MCP clients, potentially leading to data integrity issues or logic manipulation. There is no direct confidentiality or availability impact reported. The CVSS score of 5.3 reflects a medium severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed.

A patch addressing this vulnerability is available in commit 7f19b52280f414f57af2b79a95333d1c8fbeece5. Users should update APIFold to include this fix to ensure webhook payloads are properly authenticated and signature-validated. Since no official vendor advisory or patch links are provided, verify the presence of this commit or equivalent fixes in your deployed version. Patch status is not yet confirmed via vendor advisory; check the vendor's official channels for current remediation guidance.