Summary

An authenticated user with read access to Activity could influence the ORDER BY clause of the activity list endpoints by supplying an arbitrary sort column:

• GET /api/v1/fleet/activities (ListActivities)
• GET /api/v1/fleet/hosts/{id}/activities (ListHostPastActivities)

This originated from the deprecated cursor-pagination helper (appendListOptionsWithCursorToSQL), which interpolated the caller-supplied order key into SQL without an allowlist. The original report's node_key extraction scenario (/api/v1/fleet/labels/{id}/hosts) was remediated separately in #44385; these two activity endpoints were the residual call sites, neither of which joins the hosts table, so node_key was never reachable through them.

Impact

Read-only. Because the order key was interpolated, an authenticated user with Activity read could sort by columns not otherwise returned in these responses. The exposure was bounded to columns on activity_past (e.g. details on /api/v1/fleet/activities, which is not in that endpoint's SELECT; host-only activities are already excluded by WHERE host_only = false). There is no privilege escalation, write access, or reachability of node_key or other host-join columns through these endpoints.

Remediation

The deprecated helper was removed from the codebase. Both endpoints now pass the caller-supplied sort column through SanitizeColumn, which strips all characters except [\w-.] and backtick-quotes each identifier segment. This closes the injection vector: separators, whitespace, parentheses, and quotes cannot survive sanitization, so an expression-based ORDER BY oracle is not constructable.

Affected versions

< fleet-v4.89.0. Fixed in fleet-v4.89.0.

Credit

Thanks to @axel-corsiez for the report.