How do I extend an Ethernet cable at a wall socket?
Correct solution - replace the wire with a long enough wire. This plays to "why network &amp; telephone wires should always be run in conduit, always."

Kludge that will still be difficult with only an inch inside a box - put a plug on it and use a dual-jack extender.

Kludge that will work fine if you are OK with drywall and paint repairs - move the box 4" up the wall.