This is an irregular verb. It is a model verb.
PresentPresente
Pedro se avergüenza de sus errores.
Pedro is ashamed of his mistakes.
PreteritePretérito indefinido
Ana se avergonzó cuando olvidó su discurso.
Ana was embarrassed when she forgot her speech.
ImperfectPretérito imperfecto
Antes me avergonzaba de mi acento.
I used to be ashamed of my accent.