A mesaversal buffer overflow is one technique used by multiversal civilisations in order to travel between different multiverses in the metaverse.
On each step of the operations of the mesaverse, information is written to the mesaverse's memory; this is how changes actually occur inside multiverses. Ordinarily, actions performed inside a multiverse will only affect memory related to that multiverse; we call this physics. However, there are some actions, typically only accessible to a multiversal civilisation by coordinating actions over an entire multiverse, that allow actions taken inside of a multiverse to affect the memory related to other multiverses.
One analogy, though inaccurate, is if there was an 8-bit number in memory that remained between 0 and 255. If, at 255, it was incremented, a badly-designed memory storage system would set it to 0, but then set the first bit of the next byte to 1; this byte may not be part of the number being incremented, or even part of the program incrementing the number. It so happens to be that the mesaverse has a similar design flaw, but much more subtle and over the scale of multiverses.
As this is not expected behaviour of the mesaverse, done incorrectly, it can cause a harmful crash, damaging large portions of the mesaverse or even forcing a complete reset on the xeroversal level; the latter is a very bad eventuality usually prevented by the Utilities intervening in certain kinds of buffer overflows. This can be weaponised, to induce crashes in a target multiverse, but is also a risk for civilisations that have not yet built proper mesaversal buffer overflow infrastructure.