Wormholes are entirely speculative and need exotic matter with negative mass to exist. According to the optical Raychaudhuri's theorem, which describes the motion of nearby matter in curved spacetime, this requires a violation of the averaged null energy condition.

That is, wormholes defy mathematical boundaries of spacetime being positive in any particular region. Importantly, Einstein's field equations can yield unphysical solutions or things like closed timelike curves that create causality paradoxes and other strange phenomena.