CVE-2026-49869: Kestra: Unauthenticated Remote Code Execution via Authentication Bypass in `AuthenticationFilter`

Synopsis

This is an authentication bypass vulnerability in Kestra, an open-source workflow orchestration platform. A remote attacker with no credentials can exploit a flawed suffix-match path check in AuthenticationFilter to reach any API endpoint whose path ends with "/configs", bypassing Basic Auth entirely. Successful exploitation gives the attacker the ability to create and execute arbitrary workflows, which translates directly to unauthenticated remote code execution as root inside the Kestra worker container because script execution plugins are enabled by default. No fix versions have been published yet; HarborGuard is tracking the upstream advisory and will make a patched-image rebuild available the moment a fix is released.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Kestra API service over the network; any internet- or LAN-exposed Kestra instance is in scope.

• AuthenticationNot required

  No credentials of any kind are needed; the suffix-match bypass in AuthenticationFilter allows fully unauthenticated access to protected API endpoints.

• Victim interactionNot required

  The attack is fully server-side and requires no action from any user or administrator.

• Attack complexityDetail

  Exploitation is reliable and condition-free; the attacker simply crafts a request path ending in "/configs" and the filter bypass is consistently triggered.

Blast Radius

• The attacker executes arbitrary operating-system commands as root inside the Kestra worker container, giving full control of that container environment.
• All secrets, environment variables, and mounted credentials visible to the worker process are readable by the attacker.
• The attacker can create, modify, or delete Kestra workflows and their stored state, corrupting orchestration logic and persisted job data.
• Depending on network posture and mounted volumes, the attacker can pivot from the worker container to adjacent services or storage backends accessible from within the cluster.