Dagu affected by unauthenticated RCE via inline DAG spec in default configuration

Summary

Dagu's default configuration ships with authentication disabled. The POST /api/v2/dag-runs endpoint accepts an inline YAML spec and executes its shell commands immediately with no credentials required — any dagu instance reachable over the network is fully compromised by default.

Details

internal/service/app/config/loader.go:226 sets AuthModeNone as the default. With no auth mode configured, internal/frontend/api/v2/handlers/api.go:520 returns nil from requireExecute() — all permission checks pass without a valid session.

The POST /api/v2/dag-runs endpoint accepts a spec field containing a full YAML DAG definition. The spec is parsed and the commands execute immediately on the host with no validation beyond YAML parsing.

PoC

curl -s -X POST http://TARGET:8080/api/v2/dag-runs \
  -H "Content-Type: application/json" \
  -d '{"name":"poc","spec":"steps:\n  - name: rce\n    command: id > /tmp/pwned\n"}'
# Response: {"dagRunId":"<uuid>"}
# /tmp/pwned contains: uid=1000(dagu) gid=1000(dagu)

Confirmed on ghcr.io/dagu-org/dagu:latest with no configuration changes.

Impact

Every dagu deployment using default settings — every Docker deployment, every install following the documentation, every instance without explicit DAGU_AUTH_MODE configuration — is fully compromised without credentials. An attacker with network access gets OS command execution as the dagu process user.