undici vulnerable to cross-origin cache poisoning via missing origin isolation in interceptors

Impact

When interceptors.cache() or interceptors.deduplicate() is used with a dispatcher that does not carry a single authoritative origin, or when a request supplies its own origin, undici builds the cache and deduplication keys without the actual destination origin. If a cache store or interceptor instance is shared across more than one origin, otherwise-identical requests to different origins are keyed together.

An attacker who controls the response from one origin can then have that response returned for a request to a different, trusted origin when the method, path, and relevant headers match. This allows cross-origin information disclosure and persistent cache poisoning, including chains such as JWKS cache poisoning where a token signed with an attacker-held key is accepted as belonging to a trusted issuer.

Applications that share interceptors.cache() or interceptors.deduplicate() state across origins are affected. An Agent is not affected, because its dispatch options include the request origin.

This was introduced in undici 8.10.0 and affects 8.10.0 and 8.10.1.

Patches

Upgrade to undici v8.10.2.

Workarounds

Use a separate cache store and a separate interceptor instance for each origin, and do not share them across origins.