Recent developments in artificial intelligence and the internet-of-things have created great demand for low-power microelectronic devices. Two-dimensional (2D) electrical switching materials are extensively used in neuromorphic computing technology, yet their high leakage current and low endurance impede their further application. This study presents a vertical crossbar-structured conductive-bridge threshold switching device based on 2D TaSe2 oxide. Utilizing natural oxidation under air to generate a TaSeO functional layer, this device demonstrates stable electrical switching behavior with a low operating voltage (<0.8 V) and a steep turn-on slope (<9.4 mV decade–1). Notably, the device demonstrates exceptionally subattojoule energy consumption (0.142 aJ) and remarkable durability (>108). This breakthrough tackles the endurance issues prevalent in 2D devices and holds promising implications for neuromorphic computing. The fundamental switching process, as supported by transmission electron microscopy, hinges on the role of Ag2Se nanocrystalline islands in promoting the growth of conductive filaments, enhancing device performance and endurance.