There are 6 irregular verbs in the present subjunctive tense; dar, ir, ser, haber, estar, saber.
The conjugations are as follows:
Dar: dé, des, dé, demos, deis, den
Ir: vaya, vayas, vaya, vayáis, vayan
Ser: sea, seas, sea, seamos, seáis, sean
Haber: haya, hayas, haya, hayamos, hayáis, hayan
Estar: esté, estés, esté, estemos, estéis, estén
Saber: sepa, sepas, sepa, sepamos, sepáis, sepan
Although this seems a lot to remember, an easy way to remember which verbs are irregular in the subjunctive is by using the acronym DISHES.