Recently, a security vulnerability, CVE-2022-24030, has been discovered in Insyde InsydeH2O's AhciBusDxe component, which spans across kernel versions 5.1 through 5.5. This post aims to provide an in-depth understanding of the vulnerability, including a code snippet, links to the original references, and exploit details. The vulnerability lies in the SMM (System Management Mode) memory corruption, allowing attackers to write fixed or predictable data to the dedicated SMRAM (System Management RAM), potentially escalating privileges to the highly secure and privileged SMM.

Vulnerability Details

The issue affects Insyde InsydeH2O's AhciBusDxe, a component responsible for managing the AHCI (Advanced Host Controller Interface) bus in the firmware. The vulnerability arises from the improper handling of a particular memory allocation process within the SMM code, leading to memory corruption.

A malicious attacker could exploit this vulnerability by manipulating the memory allocation process during runtime, using fixed or predictable data to overwrite the contents of the SMRAM. Successful exploitation could result in the attacker gaining unauthorized access to the super-privileged SMM, potentially compromising the entire system.

Here's an example snippet of the vulnerable code in the AhciBusDxe file

// Allocate memory for SMM inside AhciBusDxe
Status = gSmst->SmmAllocatePool (
                  EfiRuntimeServicesData,
                  sizeof (EFI_AHCI_REGISTERS),
                  (VOID **)&AhciRegisters
                  );

if (EFI_ERROR (Status)) {
  return Status;
}

...

// Memory corruption occurs due to improper handling of the AhciRegisters structure
AhciRegisters = (EFI_AHCI_REGISTERS *)((UINT8 *)AhciRegisters + sizeof (EFI_AHCI_REGISTERS));

The code above demonstrates the initial allocation of memory for the AhciRegisters structure, followed by the improper manipulation of memory, which may lead to corruption in the SMRAM, if an attacker is able to exploit this flaw.

Exploit Details

Attackers can potentially exploit the vulnerability by gaining control over the firmware and manipulating the memory allocation process, leading to the writing of fixed or predictable data to the SMRAM. This could be achieved through multiple factors, such as vulnerabilities in firmware update mechanisms or other firmware components having access to the affected memory area.

Given the highly privileged nature of the SMM, a successful exploitation of this vulnerability could have severe consequences, including bypassing OS-based security controls, firmware persistence, and unauthorized access to sensitive data stored in the SMRAM.

1. CVE Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-24030

Conclusion

CVE-2022-24030 is a critical SMM memory corruption vulnerability in Insyde InsydeH2O's AhciBusDxe component, affecting kernel versions 5.1 through 5.5. Security researchers and system administrators should be aware of this vulnerability, as successful exploitation could result in elevated privileges to SMM and potential system-wide compromise. It is crucial to stay up-to-date with security patches and advisories, ensuring that firmware components are protected against known vulnerabilities.

Timeline

Published on: 02/03/2022 02:15:00 UTC
Last modified on: 03/09/2022 19:11:00 UTC