How To Replace Broken Light Junction Box in Ceiling
If you don't see any obvious screws that secure the junction box to the ceiling or side joist, you can do &quot;dental work&quot; to carefully demolish the old box, cutting it up with snips, nipper, vibrating tool or a Dremel.  Then you'll have a 4&quot; round hole in the ceiling.  Then you can install an &quot;old work&quot; box to the joist or whatever attachment point is available, or simply to the drywall itself using certain types of &quot;old work&quot; boxes.  Use a lightweight, low profile fixture that you're not likely to bash into.