What attacks can be performed by changing header of IP packet if I apply only ESPv2(so confidentiality and integrity of payload(no header integrity))?

What attacks can be performed by changing header of IP packet if I apply only ESPv2(so confidentiality and integrity of payload(no header integrity))?

What attacks can occur by altering the IP packet header with only ESPv2 (so having ONLY payload confidentiality&integrity but NOT integrity)?

My professor warns against using ESPv2 without header integrity due to potential header manipulation attacks. What can be these header manipulation attacks in this situation in which I have an ecrypted payload? What attacks can happen?