CVE-2026-3514: Authentication Bypass in prefecthq/prefect

Synopsis

An authentication bypass vulnerability exists in prefecthq/prefect versions before 3.6.22. The flaw is reachable over the network without any credentials: the authentication middleware skips auth checks on any URL path ending with 'health' or 'ready', so an attacker can create resources with names matching those suffixes and read them unauthenticated. Successful exploitation gives an unauthenticated remote attacker read access to sensitive data stored in Prefect Variables, including API keys and database credentials. A patched-image rebuild at version 3.6.22 is available on HarborGuard for affected environments.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable Prefect API is exposed over the network, so an attacker must be able to send HTTP requests to it from a remote host.

• AuthenticationNot required

  No credentials of any kind are needed; the middleware actively skips authentication for the affected URL paths.

• Victim interactionNot required

  The attacker makes direct requests to the API with no need for any user to take an action.

• Attack complexityDetail

  Exploitation is reliable and condition-free: the attacker only needs to know or guess a resource name ending in 'health' or 'ready', which they can create themselves.

Blast Radius

• Reads Prefect Variables containing stored API keys and database credentials without any prior authentication.
• Reads metadata for flows, deployments, work pools, and work queues, exposing pipeline structure and configuration details.
• Provides a foothold for further attacks using harvested credentials against downstream systems that Prefect is integrated with.