It's not exactly a virus, but last fall some folks put together a PoC showing how certain fax machines could be compromised over the phone line, and used to gain access to their connected networks. [1]
Yep, IF the FAX is connected to network (some are, some aren't) and I would be surprised (even if the researchers do state that) that a "generic" exploit (meaning ALL brand/model of all-in-ones) is possible (maybe they would need a "library" of similar exploits and test them until they find the "right" one for the given brand/model at the other end).
[1] https://blog.checkpoint.com/2018/08/12/faxploit-hp-printer-f...