Computer Weekly in the UK did some pioneering journalism into a helicopter crash[1] that had initially been blamed on the two pilots but seems very likely to have been caused by a failure of a computer system that was controlling the fuelling of the engines. Iirc this system seems to have crashed causing engine failure of both engines in heavy fog, bringing the helicopter down with a loss of everyone on board, however for reasons somewhat unclear, the MOD wanted to cover the failure up by blaming the pilots.
Now this was a windows system[2] rather than linux but the point remains - if there was an external vulnerability in a crucial control system and this system was part of a network (eg to connect telemetry) then any exploit of that system could result in loss of life.
[1] https://www.computerweekly.com/news/1280091718/Chinook-compu...
After an assessment of the Fadec software the Superintendent of Engineering Systems said that the density of deficiencies was so high that the software was unintelligible.