This vulnerability is a path‑traversal flaw (CWE-22) in the FileArtifactService of Google ADK TypeScript. Through crafted relative or percent‑encoded sequences (for example, "../" or "..%2F") supplied in the userId or sessionId parameters, an unauthenticated remote attacker can read arbitrary files that match the artifact directory layout or write files outside the intended artifact storage root. The flaw does not affect the default InMemoryArtifactService, only applications that enable the non‑default FileArtifactService exposed by the ADK API server.

The affected product is the Google ADK TypeScript library (@google/adk). Versions 0.4.0 to 0.5.x (0.4.0 before 0.6.0) are vulnerable. The vulnerability is present whenever the server is configured with the non‑default FileArtifactService enabled. Products using the default InMemoryArtifactService are not impacted.

The flaw carries a CVSS score of 9.1, indicating critical severity. The EPSS score is not available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. A remote unauthenticated attacker can exploit the flaw via network requests to the exposed API service. The attack requires only that the service be reachable and that the non‑default FileArtifactService be enabled; no additional credentials or privileged access are needed.