CommBuffer” is the name of a communication mechanism between runtime code and runtime SMM code. Malicious code could set the address of
CommBuffer such that calls to runtime SMM code would overwrite or expose the contents of SMRAM.
This issue is addressed by EDK2 SVN https://sourceforge.net/p/edk2/code/13514, 13530, and 14292.
Reported by the Advanced Threat Research team at Intel Security.