Canon's new ML-100, ML-105 industrial cameras can reach ISO 4.5 million

 https://www.dpreview.com/news/1598799167/canon-announces-two-new-industrial-use-cameras-with-extreme-low-light-capabilities

19um 35mm full-frame CMOS sensor. The sensor can capture Full HD (1080p) with a subject illumination of less than 0.0005 lux when set to their maximum 75dB gain setting (equivalent to roughly 4.5M ISO)