Uncle Sam's 40,000 top civilian and military brass who have been frozen at the $50,000 pay level for years while their subordinates' salaries crept higher may find a little something extra in their Christmas stockings this year.

Congressional leaders who want to raise top career pay but are afraid of the political backlash believe they have found a route through the legislative minefield that has blocked previous executive pay exercises.

The Senate twice has voted in favor of raising the ceiling on top career and military pay from$50,112.50 to $58,500. The House is split on the issue, with some members demanding they get a 4.8 percent raise if senior bureaucrats and military personnel get bigger raises.

This week, backers of executive raises removed the pay issue from the continuing appropriation bill before the president vetoed it. Yesterday Reps. Mike Barnes (D-Md.), Steny Hoyer (D-Md.) and Frank Wolf (R-Va.) met and worked out a plan they hope will make the raises a reality by Dec. 15 when the current continuing resolution runs out.

Idea is to give House members a chance to vote on a pay raise for themselves (but not for senators) and then, if that loses, to vote separately on raising the pay ceiling for executive branch officials and military personnel.

The vehicle is language, already cleared by the Senate, written by Assistant Majority Leader Ted Stevens (R-Alaska) with help from the Senior Executives Association. The Stevens amendment would raise the pay ceiling for supergraders (in Grades 16, 17 and 18) to $57,500, and raise the maximum salary for members of the Senior Executive Service to $58,500. If that ceiling is lifted, workers in Grades 14 through Grade 18 who now are limited to $50,112.50 would be allowed to rise anywhere from a few hundred dollars a year to more than $8,000 a year at top levels.

It will be mid-December before Congress tackles the executive pay issue again. But the Senate has cleared it twice already, and there is a better than even chance the House will do likewise this time around. The Reagan administration is supporting the executive pay raises.