NaN/INF in serverbound movement packets can crash clients and servers

Summary

### Impact A malicious client may send a `MovePlayerPacket` to the server whose position or rotation contains NaN or INF. Since neither the server nor vanilla client handles this properly, a number of interesting side effects come into play. - The server may crash in various ways if this exploit is used, because some mathematical operations on NaN/INF generate PHP warnings, which are converted into exceptions. - Clients may not be able to see other clients who have a NaN/INF rotation. - Clients may also crash in such cases. ### Patches A patch for this was included in the 3.18.1 release: https://github.com/pmmp/PocketMine-MP/commit/fb20bb38327b4c08ee3976640cd0dd547388a638 ### Workarounds Workarounds could be implemented as plugins using `DataPacketReceiveEvent` to block any inbound movement packets containing bogus values. ### For more information If you have any questions or comments about this advisory: - Open an issue in [pmmp/PocketMine-MP](https://github.com/pmmp/PocketMine-MP) - Email us at [[email protected]](mailto:[email protected])