CVE-2026-48119: Nezha's authenticated agents can forge service-monitor results for other users' services

Nezha accepts service-monitor TaskResult messages from an authenticated agent based only on whether the reported service ID exists. The dashboard authenticates the agent and derives the reporter server ID from the gRPC stream, but the service-monitor result worker does not verify that the reporter server was selected for that service, belongs to the service owner, or was actually assigned that monitoring task.

A low-privilege user with a valid agent secret and one registered agent can therefore submit forged monitoring results for another user’s service ID. This allows cross-tenant corruption of service-monitor history/current state, and can influence victim-owned service notifications with attacker-controlled result text.