Heat olive oil in a large saucepan over medium heat. Add leek, carrots, zucchini, green beans, and celery. Cover, reduce the heat to low, and cook for 15 minutes, shaking the pan occasionally.
Uncover and stir in stock, tomatoes, and thyme; bring to a boil. Cover again, reduce the heat to low, and simmer gently for 30 minutes.
Stir in undrained cannellini beans and pasta. Simmer for an additional 10 minutes, or until pasta is tender yet firm to the bite. Season with salt and pepper before serving.
