I would say somewhat dangerous. If the brake will not function you can't stop powering in on a hill/slope unless your in a position to hold yourself with the vehicles brakes. Or if the vehicle your recovering can do the same.
Park yourself on a hill and play with it to get an idea. Stay in the drivers seat so you can use your brakes when needed. Its still better than no winch but I'd fix is asap.
Speski OffRoad LTD, Cargo Solutions for Toyota 4x4's http://www.SpeskiOffRoad.com
"80 series, with a fridge"
1976 FJ40, Project with little progress.
2004 Starcraft 10RT