A recently discovered critical vulnerability, CVE-2022-31243, has been found to cause SMRAM corruption in the FvbServicesRuntimeDxe driver. This vulnerability is related to Direct Memory Access (DMA) transactions, which are targeted at input buffers utilized by the Software System Management Interrupt (SMI) handler, resulting in a Time-Of-Check-To-Time-Of-Use (TOCTOU) attack. Insyde engineering discovered this issue based on the general description provided by Intel's iSTARE group.

Original References

For more information on this vulnerability, you can visit Insyde's Security Pledge page, where they provide a detailed description and update on the issue: https://www.insyde.com/security-pledge/SA-2022044

In addition to visiting Insyde's Security Pledge page, it is also essential to stay updated on the Linux Kernel versions that address this vulnerability. The Linux Kernel versions 5.2 (Kernel 5.2: 05.27.21), 5.3 (Kernel 5.3: 05.36.21), 5.4 (Kernel 5.4: 05.44.21), and 5.5 (Kernel 5.5: 05.52.21) have fixed the issue.

Exploit Details

The main issue of CVE-2022-31243 arises when DMA transactions target the input buffers, which are used for the SMI handler in the FvbServicesRuntimeDxe driver. The targeted input buffers can potentially corrupt the SMRAM and lead to a TOCTOU attack.

The following code snippet demonstrates how an attacker could potentially exploit the vulnerability

import numpy as np

# Define a function to simulate a DMA transaction
def dma_transaction(input_buffer, data):
    # Target the input buffer used for the SMI handler
    input_buffer[:] = data[:]

# Define a function to simulate the SMI handler
def smi_handler(input_buffer):
    # Check if the data in the input buffer is valid
    if is_valid_data(input_buffer):
        # Perform the DMA transaction
        dma_transaction(input_buffer, get_evil_data())

# Define a function to check if the data in the input buffer is valid
def is_valid_data(data):
    # Checking conditions
    return (data[] > ) and np.all(data[1:] > data[:-1])

# Define a function to obtain the evil data
def get_evil_data():
    # Load the evil data from a file, or otherwise retrieve it
    return np.array([5, 10, 20], dtype=np.uint32)

# Simulate the attack
input_buffer = np.array([3, 6, 12], dtype=np.uint32)

By understanding the exploit details, it is crucial to mitigate this vulnerability to protect systems from potential malicious attacks.


CVE-2022-31243 is a critical vulnerability that can cause SMRAM corruption in the FvbServicesRuntimeDxe driver due to targeted DMA transactions at input buffers. The Linux Kernel has addressed this issue in versions 5.2, 5.3, 5.4, and 5.5. Applying the patches and staying informed about the latest security findings is vital in protecting your system.


Published on: 11/15/2022 00:15:00 UTC
Last modified on: 02/14/2023 12:15:00 UTC