Vyasasmriti 1.8

1.8

vaiśyāsu viprakṣattrābhyāṃ tataḥ śūdrāsu śūdravat
adhamāduttamāyāntu jātaḥ śūdrādhamaḥ smṛtaḥ

Upon Vaiśya women by a brahmin or Kṣatriya [it is performed accordingly], and thereafter upon Śūdra women, like a Śūdra.
One born from a lower [man] upon an upper [woman], however, is remembered as lower than a Śūdra.