I'd say very slim - The boards within eNodeB/NodeB's that process RF traffic typically do not run a Linux base on them (in my experience) FPGA's and dedicated A

I'd say very slim - The boards within eNodeB/NodeB's that process RF traffic typically do not run a Linux base on them (in my experience) FPGA's and dedicated ASICS are far more likely. You'll typically find it's only the controller board within your base station that as a Linux OS running within, user plane traffic at this point is just traversing the board as normal IP traffic so no interactions with bash are required, there is some signalling plane traffic (mainly LTE) however the majority of that is within the NAS which is eNodeB transparent. I'd guess the biggest concern would be the MME's processing of signalling messages, as basically all the boards within these systems will generally be Suse/RedHat based. However again there's going to be a very slim chance of bash injection, most of signalling modules are C++ based and don't have a requirement for bash, and even if they did implement bash for some unknown reason there is masses of validation applied to the signalling variables leaving very little room for an injection payload.