If you use OS-level virtualization solution (sandboxes, containers, selinux), the malware can use local privilege escalation exploit.
If you use hardware virtualization the malware can exploit vulnerabilities in the hypervisor (and other underlying software including OS, bios and firmwares (a lot of devices have firmwares flashable, this allow creation of extremely persistent rootkits)) and fault injection like RowHammer.
If you use an emulator, the malware can try to exploit a vulnerability in the emulator.
So you need a separate physical machine and if you need to analyse binaries automatically you need the software on the analysing machine to be not vulnerable.
Now forget everything written above because it is not a real life scenario (unless you are high-value target for intellegence agencies). A hardware virtualization solution (for example QubesOS) should be enough, if you cut it from devices (no OpenGL passthrough, no PCI passthrough, no USB passthrough, no access to storage, etc ...)