just picked it up from Ubuntu package.
Fixed in 376fc9d22f1480ac380a3845f4cb4fe227e4be9a
Author: Akira TAGOH <email@example.com>
Date: Tue Nov 20 20:09:10 2012 +0900
Bug 57286 - Remove UnBatang and Baekmuk Batang from monospace in 65-nonlatin
Those two fonts are serif fonts. shouldn't be added to monospace.