GHSA-m4q3-457p-hh2x

1. Vulnerability Summary

The dagRunId request field accepted by the inline DAG execution endpoints is passed directly into filepath.Join to construct a temporary directory path without any format validation. Go's filepath.Join resolves .. segments lexically, so a caller can supply a value such as ".." to redirect the computed directory outside the intended /tmp/<name>/<id> path. A deferred cleanup function that calls os.RemoveAll on that directory then runs unconditionally when the HTTP handler returns, deleting whatever directory the traversal resolved to.

With dagRunId set to "..", the resolved directory is the system temporary directory (/tmp on Linux). On non-root deployments, os.RemoveAll("/tmp") removes all files in /tmp owned by the dagu process user, disrupting every concurrent dagu run that has live temp files. On root or Docker deployments, the call removes the entire contents of /tmp, causing a system-wide denial of service.

2. This Is Not a Duplicate of Existing Advisories

Two security advisories are already published for dagu. This vulnerability is distinct from both.

GHSA-6qr9-g2xw-cw92 fixed the fact that the default authentication mode was none, allowing unauthenticated access to the inline execution endpoint. That advisory covers authentication bypass. The dagRunId path traversal described here is a separate input-validation flaw in loadInlineDAG() that exists regardless of whether authentication is required and was not addressed by that fix.

CVE-2026-27598 fixed a path traversal in the DAG creation endpoint (POST /api/v1/dags) via the name field. The fix added filepath.Base() and a base-directory prefix check inside generateFilePath(). That fix applies only to generateFilePath() in dags.go. The function loadInlineDAG() in dagruns.go has no equivalent guard on its dagRunID argument and was not part of that patch.

3. Vulnerable Code

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