I was afraid of this! The quick and dirty way to try to stop the leak is loosening the threaded bulkhead locking collar a turn or two, then retighten…
In the 50/50 shot that this doesn’t work; the next step would be to remove the bulkhead locking collar, and cut the 1.5” pipe… this lets you remove the bulkhead and standpipe from the overflow box… then, you can thoroughly clean the glass around the bulkhead hole, in addition to the bulkhead fitting/gasket themselves! — from there; a little silicone lubricant, and reinstall…
Gold standard fix would be replacing the bulkhead fitting completely… ideally with a gasket which has a ridge in its radius to provide more sealing pressure along the ridge(s)!
Example: