CVE-2026-103036: @orpc/json-schema: Prototype injection in smart coercion
oRPC is a tool that helps build APIs that are end-to-end type-safe and adhere to OpenAPI standards. Prior to 1.14.9, the @orpc/json-schema SmartCoercionPlugin uses JsonSchemaCoercer to collect object properties in a plain object and to resolve schema.properties entries through the prototype chain. A remote client that can reach a procedure with an object input schema can supply proto to replace the prototype of the single coerced request object, or supply Object.prototype member names such as constructor and toString so inherited values are treated as sub-schemas and pass the coercer's satisfaction check. Attacker-controlled inherited properties can consequently affect handler, Object.assign, or configuration lookups, while legitimate proto properties are dropped. The global Object.prototype, unrelated objects, other requests, and other users are not modified, and downstream schema validation still runs. This issue is fixed in version 1.14.9.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
@orpc/json-schemato a version that resolves this vulnerability.Fixed in 1.14.9
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using @orpc/json-schema before version 1.14.9 are affected when a remote client can reach a procedure that accepts an object input schema. The issue is reachable over the network without authentication or user interaction according to the supplied vector.
What input is needed to trigger the behavior?
An attacker can provide __proto__ in an object input to replace the prototype of the single coerced request object. They can also use Object.prototype member names, such as constructor or toString, causing inherited values to be handled as sub-schemas by the coercer.
What is the scope of the prototype modification?
The global Object.prototype, unrelated objects, other requests, and other users are not modified. The impact is limited to the single coerced request object, although its attacker-controlled inherited properties can affect handler, Object.assign, or configuration lookups.
Does downstream validation prevent exploitation?
Downstream schema validation still runs, but the coercer's prototype-chain resolution can allow inherited values to pass its satisfaction check. Legitimate __proto__ properties are dropped.
What remediation is available?
Upgrade @orpc/json-schema to version 1.14.9, which fixes the issue.