What are the legal implications of a mother accusing her son of being a child of fornication, and what should the son do in such a situation?

The mother's impugning her child's lineage and confessing to zina (unlawful sexual intercourse) herself is a grave and Islamically forbidden reprehensible act, whether she is lying or truthful. This is because impugning lineages and boasting about ancestries are practices of the pre-Islamic era (Jahiliyyah), and because Allah has commanded self-concealment and not self-exposure. The mother's statement has no bearing on the child's lineage, for the child belongs to the marital bed, and their lineage is not denied except through li'an (oath of condemnation) from the father, even if the mother admits to zina. Nevertheless, the mother's right to kindness and good treatment is not forfeited. One must be kind to her and not abandon her, even if she has erred. It is recommended to accompany her with good conduct, and if it is possible to move to another place to avoid people's harm, that would be better.