Gita talks about Vedas
BG 10.22: I am the Sāma Veda amongst the Vedas, and Indra amongst the celestial gods. Amongst the senses I am the mind; amongst the living beings I am consciousness.
It also talks about Brahma Sūtra.
BG 13.5: Great sages have sung the truth about the field and the knower of the field in manifold ways. It has been stated in various Vedic hymns, and especially revealed in the Brahma Sūtra, with sound logic and conclusive evidence.
But does the Gita talks about Upanishads or mention it?