The vehicle was pulled over near Junction 15 and herbal cannabis was discovered with a street value of around £50,000.
Two men, aged 19 and 20, were arrested and charged in connection with the incident.
They are due to appear at Dumfries Sheriff Court on Monday June 21.
Sergeant Jonathan Edgar from Dumfries & Galloway Road Policing said: “This is a significant amount of drugs that have been taken off the streets by our officers.
“These now cannot be sold, and prevent harm being caused in our communities.”