A vulnerability in mintplex-labs/anything-llm prior to version 1.3.1 allows for path traversal due to improper handling of non-ASCII filenames in the multer library. This vulnerability can lead to arbitrary file write, which can subsequently result in remote code execution. The issue arises when the filename transformation introduces '../' sequences, which are not sanitized by multer, allowing attackers with manager or admin roles to write files to arbitrary locations on the server.
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize '\..\filename' (leading backslash dot dot) sequences that can resolve to a location that is outside of that directory.