The vulnerability is a directory traversal flaw (CWE-22) that allows an unauthenticated attacker to read arbitrary .jsonl files residing on the server’s filesystem. The dashboard HTTP server exposed two endpoints, /api/session-summary and /api/session-events, which accepted a sessionId query parameter. The parameter value was concatenated directly into a file path using path.join, and Node.js normalized the .. segments during resolution, thereby enabling the attacker to craft a request that walks outside the intended directory and retrieves any readable JSONL file. The impact is a breach of confidentiality, as attackers can obtain sensitive log data without needing credentials or elevated privileges. No execution or denial‑of‑service impact is disclosed.

The affected product is Token Optimizer MCP by ooples. All releases before version 5.1.0 contain the flaw. Version 5.1.0 and later include the patch that removes the unauthenticated endpoints or adds proper authentication.

The CVSS score of 5.3 indicates moderate severity. EPSS is not available, and the flaw is not listed in the CISA KEV catalog, suggesting no known large‑scale exploits. The attack requires only network access to the dashboard server and the ability to craft a URL with a sessionId query string. An attacker could therefore read potentially sensitive session logs from a remote machine, but would need no additional privileges or code execution capability. The overall risk is moderate, with the primary concern being confidentiality exposure of log files.