yt-grabber-tui local arbitrary file overwrite via TOCTOU race in config file creation

Summary

yt-grabber-tui is a C++ terminal user interface application for downloading YouTube content. yt-grabber-tui version 1.0 contains a Time-of-Check to Time-of-Use (TOCTOU) race condition (CWE-367) in the creation of the default configuration file config.json. In version 1.0, load_json_settings in Settings.hpp checks for the existence of config.json using boost::filesystem::exists and, if the file is missing, calls create_json_settings which writes the JSON configuration with boost::property_tree::write_json. A local attacker with write access to the application’s configuration directory (~/.config/yt-grabber-tui on Linux or the current working directory on Windows) can create a symbolic link between the existence check and the subsequent write so that the write operation follows the symlink and overwrites an attacker-chosen file accessible to the running process. This enables arbitrary file overwrite within the privileges of the application process, which can corrupt files and cause loss of application or user data. If the application is executed with elevated privileges, this could extend to system file corruption. The issue is fixed in version 1.0.1.