CVE-2026-32621: Apollo Federation vulnerable to prototype pollution via incomplete key sanitization

A vulnerability exists in query plan execution within the gateway that may allow pollution of Object.prototype in certain scenarios. A malicious client may be able to pollute Object.prototype in gateway directly by crafting operations with field aliases and/or variable names that target prototype-inheritable properties. Alternatively, if a subgraph were to be compromised by a malicious actor, they may be able to pollute Object.prototype in gateway by crafting JSON response payloads that target prototype-inheritable properties.

Because Object.prototype is shared across the Node.js process, successful exploitation can affect subsequent requests to the gateway instance. This may result in unexpected application behavior, privilege escalation, data integrity issues, or other security impact depending on how polluted properties are subsequently consumed by the application or its dependencies. As of the date of this advisory, Apollo is not aware of any reported exploitation of this vulnerability.