My boss quit about 9 months back, and he is not being replaced. Instead, I am taking on his jobs because I am the most senior among the team. Is it right for me to ask for a promotion or raise?

Let's go counter Intuitive.

Is it wrong for you to ask for promotion or a raise? Do hone your negotiation skill while also asking for the promotion and pay raise.

YES! please fight for yourself in terms of raise and promotion!

I think in general, a lot of the newcomers in workplaces are apprehensive or shy to ask for things for themselves!

While you don't have to come across as entitled and demand it to happen right away, you can discuss this with the boss' boss or even the HR team on the right way to approach it.

Yes. It Also depends.

It is common to work above your station as well as take on more as a form of trial of whether you can handle it.

Also consider maybe your boss role is an extra

Promotion comes later.

If it has been 6 months and there's substantial efforts to take on the extra load, totally yes.