oRPC is an tool that helps build APIs that are end-to-end type-safe and adhere to OpenAPI standards. Prior to version 1.13.6, a prototype pollution vulnerability exists in the RPC JSON deserializer of the @orpc/client package. The vulnerability allows unauthenticated, remote attackers to inject arbitrary properties into the global Object.prototype. Because this pollution persists for the lifetime of the Node.js process and affects all objects, it can lead to severe security breaches, including authentication bypass, denial of service, and potentially Remote Code Execution. This issue has been patched in version 1.13.6.

Affected: npm: @orpc/client

### Summary A critical Prototype Pollution vulnerability exists in the RPC JSON deserializer of the `@orpc/client` package. The vulnerability allows unauthenticated, remote attackers to inject arbitrary properties into the global `Object.prototype`. Because this pollution persists for the lifetime of the Node.js process and affects all objects, it can lead to severe security breaches, including authentication bypass, denial of service, and potentially Remote Code Execution.

### Vulnerability Details The root cause lies in the `deserialize()` method of `StandardRPCJsonSerializer`. When processing attacker-controlled path segments from the `meta` and `maps` arrays, the deserializer fails to implement validation or sanitization for dangerous JavaScript object keys, specifically `__proto__` and `constructor`:

https://github.com/middleapi/orpc/blob/819ed2e0897b18a5d6a4ca85ba68568f055004a1/packages/client/src/adapters/standard/rpc-json-serializer.ts#L137-L213

There are two primary distinct write vectors available to an attacker:

1. The `meta` vector: Writes type-constrained values (e.g., `Map`, `Set`, `Date`) to arbitrary object paths. 2. The `maps` vector: Allows the injection of arbitrary string values. This occurs because the return value of `getBlob(i)` (which relies on `FormData.get(i.toString())`) is cast `as Blob`. Since this is strictly a TypeScript compile-time cast, the runtime execution allows standard text fields to return as arbitrary strings.

Crucially, this des…