A stop-sale order found by Corvetteactioncenter.com indicates that the 2020 and 2021 Corvettes are suffering from a brake-by-wire issue.
GM has informed the National Highway Traffic Safety Administration and a recall is upcoming, according to the stop-sale order. The document also indicates that model year 2020 Cadillac CT4, CT5, XT4s, 2021 Chevrolet Trailblazers, and 2020-2021 Encore GXs are also affected by the stop sale.
The cause of the issue is a material used in the manufacturing process of sensor connectors may cause a communication breakdown in the brake boost system. 
According to the document, symptoms of the issue include loss of brake boost assist, a warning light and a message in the instrument panel. Loss of brake boost pressure requires the driver to step on the brake pedal much harder. If this happens all without warning, it could meaningfully increase the risk of a crash.
Dealers will replace the electronic brake boost module, according to the document posted to corvetteactioncenter.com. If the document is correct, the usual recall process will follow with owners receiving letters and going into the dealership for a free repair.