SAFETY FIRST: Protective gloves and eyewear are recommended at this point.
When a fastener has stripped the threads it should engage the best fix is often a thread insert. The idea is drill out the hole using a specific size drill bit, use a tap to create new threads and then install the thread insert. The inside diameter of the insert will be the same as the original hole allowing the fastener to be installed and properly tightened. In many cases the thread insert is stronger than the original threads.
There are many options for thread inserts, once the insert is selected make sure to follow the manufacturers specific instruction. Make sure to have a plan in place to capture any metal shavings while performing the repair.