Insyde's Security Pledge

[EDK2] MdeModulePkg/PiSmmCore: SmmEntryPoint underflow.

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVE-2021-38578

Existing CommBuffer checks in SmmEntryPoint will not catch underflow when computing BufferSize.

Kernel 5.0: Version 05.0A.03
Kernel 5.1: Version 05.18.03
Kernel 5.2: Version 05.28.03
Kernel 5.3: Version 05.37.03
Kernel 5.4: Version 05.44.53
Kernel 5.5: Version 05.52.53