Fleet has observer-level enrollment secret extraction via ORDER BY oracle on labels host-listing endpoint

Summary

Fleet is an open-source device management platform built on osquery. In versions up to and including 4.84.1, the labels host-listing endpoint (GET /api/v1/fleet/labels/{id}/hosts) allowed an authenticated user with the lowest-privilege Observer role to extract host enrollment secrets through a sort-order oracle. The endpoint accepted a user-supplied order_key parameter that was not validated against a column allowlist, so an attacker with Global or Team Observer access could set the sort column to a sensitive field such as h.node_key and combine it with the cursor-based after parameter to binary-search the value one character at a time; the targeted value never appeared in the response, but the presence or absence of results revealed each character. Because node_key and orbit_node_key are the long-lived shared secrets that osquery and Orbit agents use to authenticate to the Fleet server, an attacker who reconstructed them could impersonate enrolled hosts, submit fabricated query results and inventory, retrieve pending scripts and MDM commands, and poison compliance and policy results across the deployment. This issue is fixed in version 4.84.2.