PYSEC-2026-2285

Streamlit is a data oriented application development framework for python. Streamlit Open Source versions prior to 1.54.0 running on Windows hosts have an unauthenticated Server-Side Request Forgery (SSRF) vulnerability. The vulnerability arises from improper validation of attacker-supplied filesystem paths. In certain code paths, including within the `ComponentRequestHandler`, filesystem paths are resolved using `os.path.realpath()` or `Path.resolve()` before sufficient validation occurs. On Windows systems, supplying a malicious UNC path (e.g., `\\attacker-controlled-host\share`) can cause the Streamlit server to initiate outbound SMB connections over port 445. When Windows attempts to authenticate to the remote SMB server, NTLMv2 challenge-response credentials of the Windows user running the Streamlit process may be transmitted. This behavior may allow an attacker to perform NTLM relay attacks against other internal services and/or identify internally reachable SMB hosts via timing analysis. The vulnerability has been fixed in Streamlit Open Source version 1.54.0.