How can a process try to access other process’s memory in Linux virtual memory system

Just got confused when I am learning the virtual memory system in Linux.

Since each process has its own virtual address space and its own page table translating its virtual address to physical address(am I right?), how can it possibly try to falsely access other process’s memory? There should be no entry in the page table, right?

Answer

Unless specifically arranged, there should be no virtual address one process can access that will modify memory assigned to another process.