It is a server‑side request forgery in Streamlit Open Source that lets an unauthenticated attacker supply a UNC path. The server resolves the path with os.path.realpath or Path.resolve before validating it, causing the Windows process to open an SMB connection on port 445. During OS authentication the Windows user’s NTLMv2 credentials are sent, allowing an attacker to perform an NTLM relay attack against internal services or map usable SMB hosts timing‑wise. The flaw is classified as CWE‑918 and enables credential theft rather than direct code execution.

All Streamlit Open Source deployments running on Windows that use a version earlier than 1.54.0 are affected. The issue occurs in the ComponentRequestHandler code path that handles arbitrary filesystem paths requested by users. Any instance that exposes the default HTTP port to the network and accepts user‑supplied paths may be vulnerable.

The CVSS base score is 4.7, indicating medium impact, while the EPSS score is below 1 % and the vulnerability is not listed in CISA’s KEV catalog. Exploitation requires making an unauthenticated HTTP request to the Streamlit server with a crafted UNC path; no privileged shell or memory corruption is needed. Therefore the likelihood of exploitation is currently low, but because the vulnerability leaks NTLM credentials it poses a significant risk if the host is in an internal network with other services.