The vulnerability lies in knowns versions older than 0.31.0, where the /api/opencode proxy fails to validate the x‑opencode‑directory HTTP header. An attacker can supply an arbitrary directory path in this header, and the server will use it when performing file operations outside the intended project root. This uncontrolled path traversal flaw (CWE‑73) can allow an attacker to read, modify, or delete arbitrary files, elevate privileges, or execute code on the host machine.

This issue affects the open‑source data‑analysis tool knowns, maintained by knowns‑dev. Any installation running a release predating v0.31.0 is vulnerable, regardless of operating system or architecture.

The CVSS score of 9.3 indicates a severe impact. The EPSS score is not reported, but the lack of authentication requirements and the ability to supply the malicious header in a simple HTTP request mean the vulnerability can be exploited from a public reachable endpoint. The vulnerability is not yet listed in the CISA KEV catalog, but its high severity and broad applicability make it a high‑priority exposure.