Vulnerability relates to how you take fire damage (you take double damage), but it has no effect on your ability to use fire, so RAW there is no impact on your spellcasting.
But, say if you were to cast fireball and you were also in the area of effect, you would take the double damage even though it was your spell
Recently was "cursed" with vulnerable to fire, and could not see if I could still use my fire based spells as a cleric. Any input would be nice.
Vulnerability relates to how you take fire damage (you take double damage), but it has no effect on your ability to use fire, so RAW there is no impact on your spellcasting.
But, say if you were to cast fireball and you were also in the area of effect, you would take the double damage even though it was your spell
While it has no effect on you, if it was me I'd roleplay the heck out of being terrified of my own fire spells.