Can a herniated disc become septic?

No: A herniated disc is not likely to get infected unless the patient has a systemic infection. In that case, it is called discitis.

Unlikely: A herniated disc refers to a disc which is protruding beyond its normal boundaries. Sepsis refers to an infection which has spread into the bloodstream and therefore throughout the body. It would be possible for a herniated disc to develop an infection, and eventually lead to sepsis, but this would be a rather unlikely scenario.

It can: however that is rare, unless you are an IV drug user, had recent surgery or spine procedure or are septic in your bloodstream in general.