External master cylinder/vacuum booster leak

[tucsonjwt]

I have a leak between the master cylinder and vacuum booster. The leak appears to be where the master cylinder connects to the booster. I had leaking at the top of the master cylinder, but I replaced the seal under the master cylinder lid and the leaking stopped from that area. I have had master cylinders leak internally, but never externally. I sugged up the two nuts attaching the master cylinder but it did not stop the leak.

Is there a fix other than replacing both the master cylinder and the booster? These are AC Delco units, which only have about 30K miles. The brake fluid level is OK and the brakes work fine, and the brake light is not lit on the dash.