Because the mergeDeep function recursively traverses inherited properties, an attacker can coerce the merge logic to traverse into core JavaScript object prototypes. By supplying crafted subgraph responses, the attacker can overwrite critical built-in properties like Function.prototype.call. This action corrupts the Node.js process environment, resulting in a persistent denial-of-service condition that impacts all subsequent requests until the service is restarted. This is a highly accessible vector as it requires only a single unauthenticated query against any gateway performing standard subgraph object merging.

Impact

The vulnerability results in a total denial-of-service for the affected GraphQL gateway. Because the exploitation modifies core language primitives in the Node.js process memory, the crash is process-wide and persistent. Successful exploitation halts the processing of all incoming traffic, affecting services that rely on federated GraphQL schemas, such as Hive Gateway.

Recommendation

Prioritized actions for engineering and security teams:

• Upgrade @graphql-tools/utils to a version beyond 12.0.0 immediately to include the patch implemented in PR #8423.
• If using Hive Gateway, upgrade to the version incorporating the mitigation in PR #2600.
• Implement request validation to filter or block GraphQL queries containing aliases targeting reserved JavaScript object keys such as __proto__, constructor, or prototype in field selection sets.