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CVE-2026-49869 – Unauthenticated RCE via Authentication Bypass – Kestra prior to 1.0.45 / 1.3.21

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Summary

CVE-2026-49869 is a critical (CVSS 10.0) unauthenticated Remote Code Execution vulnerability in Kestra, an open-source event-driven workflow orchestration platform. The flaw resides in Kestra’s AuthenticationFilter, where a suffix-based path check used to whitelist the public configuration endpoint can be trivially abused to bypass Basic Auth on any API path — enabling unauthenticated workflow creation and execution. Because Kestra ships with shell and script execution plugins enabled by default, this authentication bypass directly and immediately results in unauthenticated RCE as root inside the Kestra worker container. All versions prior to 1.0.45 and 1.3.21 are affected.

Technical details

  • Root cause: In webserver/src/main/java/io/kestra/webserver/filter/AuthenticationFilter.java, the filter whitelists the public configuration endpoint using a suffix match: request.getPath().endsWith("/configs"). This is not an exact path match — any API path whose final segment is configs bypasses authentication entirely, exposing FlowController, ExecutionController, KVController, and other controllers to unauthenticated access.
  • Trigger conditions: No authentication, no special privileges, and no user interaction are required. The target Kestra instance need only be network-reachable. Attack complexity is low.
  • Attack vector: A remote, unauthenticated attacker sends an unauthenticated PUT request to create a workflow with a namespace or flow ID named configs (e.g., /api/v1/main/flows/tutorial/configs) embedding arbitrary shell commands, then triggers execution via a POST to /api/v1/main/executions/tutorial/configs.
  • Impact: Because Kestra ships with script execution plugins (plugin-script-shell, plugin-script-python, etc.) enabled by default, the created workflow executes attacker-controlled OS commands as root inside the Kestra worker container. This enables full container compromise, secret and credential theft, SSRF against internal services and cloud metadata endpoints, audit log destruction, and — where the Docker socket is accessible — full host takeover.

Affected software

  • Kestra OSS — all versions prior to 1.0.45 (1.0.x line)
  • Kestra OSS — all versions prior to 1.3.21 (LTS 1.3.x line), i.e., versions up to and including 1.3.20

Severity

CVSS v3.1 Base Score: 10.0 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate — patch: Upgrade to Kestra 1.0.45 (OSS 1.0.x line) or Kestra 1.3.21 (LTS 1.3.x line), which replace the suffix match with an exact path check, closing the authentication bypass.
  • If immediate patching is not feasible: Restrict network access to the Kestra REST API and web UI so that only trusted internal IP ranges can reach the service. Do not expose Kestra directly to the public internet until the patch is applied.
  • Additional hardening: Audit existing workflows and execution logs for evidence of unauthorized workflow creation involving namespace or flow IDs named configs, and review worker container permissions to minimize the blast radius of any container-level compromise.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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