Power booster is bad or the vacuum supply to booster is cut off.
The brake pads could be worn out
Could be low on brake fluid which indicates your brakes need attention. Have a trusted mechanic inspect the brakes NOW!
There could be an issue with the anti lock brakes if it equipped with them. It could also be that the brake fluid is low or the switch for the emergency brake is broken.
Could be contaminated brake fluid
have you checked your brake fluid??
Could be low on brake fluid, time to have the brakes checked.
If a calliper is "hanging", it could be causing the brake pads to press against the rotor and overheat the brakes. You may want to see if the calliper is dragging.
Could be a couple of different possibilities. If u have disc brakes it could be wear tabs letting you know brake pads need to be replaced or there is a light glazing or brake dust on shoe or pad
Could be a few causes of that symptom, but most likely air in the brake lines or moisture in the brake fluid. Start by replacing the brake fluid in the reservoir and bleeding the brakes.
If the brakes on a Mazda 6 are squeaking, it could be indicative of a problem. The brake pads could be incorrectly set.
It could be low on brake fluid, a sign of trouble. Have the brakes checked SOON!
The road surface could be slippery, your brake pads could be worn, your tyres could be worn, your brakes could be faulty.