CVE-2026-47120: Nezha Monitoring: RoleMember can fire other users' cron tasks via AlertRule.FailTriggerTasks (no ownership check)

createAlertRule and createService (and their update* siblings) accept FailTriggerTasks []uint64 and RecoverTriggerTasks []uint64 — IDs of cron tasks to fire when the alert/service trips. The validation function only validates the alert’s Rules.Ignore server map; it never checks that the cron task IDs in FailTriggerTasks / RecoverTriggerTasks belong to the caller.

When the alert fires, singleton.CronShared.SendTriggerTasks(taskIDs, triggerServer) (service/singleton/crontask.go:113-127) looks up those task IDs in the global cron registry and executes them via CronTrigger. For non-AlertTrigger cover modes, CronTrigger fans the command out to every server in ServerShared.Range with no ownership check.

Net effect: a RoleMember can attach their alert rule (or service monitor) to another user’s cron task ID — including admin’s crons. When the alert trips, the admin’s cron command runs across every server (or every server in its allow/deny list).

This is the same fanout/auth-bypass class as NEZHA-002 (cron creation), but reachable by a different code path: even if /cron writes are restricted to admin, this /alert-rule and /service writes are member-reachable and let a member invoke pre-existing admin crons.