BRLY-2021-038

The heap buffer overflow vulnerability in child SW SMI handler on multiple HP devices.

Public Disclosure Date: Mar 8, 2022

CVE ID

CVE-2022-23930

[Device](https://support.hp.com/us-en/drivers/selfservice/hp-prodesk-405-g6-small-form-factor-pc/38230306) / firmware version: `02.05.01 Rev.A`

Summary

BINARLY efiXplorer team has discovered a heap buffer overflow vulnerability in the child SW SMI handler on multiple HP devices that allows heap data corruption.

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Potential Impact

An attacker can exploit this vulnerability to elevate privileges from ring 0 to ring -2, execute arbitrary code in System Management Mode - an environment 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 BIOS. Such a malicious firmware code in BIOS could persist across operating system re-installs. Additionally, this vulnerability potentially could be used by malicious actors to bypass security mechanisms provided by UEFI firmware (for example, Secure Boot and some types of memory isolation for hypervisors).

Vulnerability Information

BINARLY internal vulnerability identifier: BRLY-2021-038
HP PSIRT assigned CVE identifier: CVE-2022-23930
CERT/CC assigned case number: VU#683814
CVSS v3.1 8.2 High AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Table of Contents

01.Affected HP firmware

02.Vulnerability description

03.Disclosure timeline

04.Acknowledgements

Affected HP firmware

Device/Firmware	File Name	SHA256 (File PE32 section)	File GUID
Device / firmware version: `02.05.01 Rev.A`	0193	40b09ebb66f7bf702edaaccb08a3f4a5ae96d1f08e1b14cb33b9341d6539fee2	12D06948-6569-42C9-ABA3-E12BACE7B234

Vulnerability description

The vulnerability exists in child the SW SMI handler registered with GUID 4dd19464-68d5-4c6d-9a6f-a6049afed855 and located at offset 0x19A0 in the driver.

It should be noted, that the HandlerType is a stack variable in this case:

.text:000000000000160D                 mov     [rbp+HandlerType.Data1], 4DD19464h
.text:0000000000001614                 ...
.text:000000000000161B                 mov     dword ptr [rbp+HandlerType.Data2], 4C6D68D5h
.text:0000000000001622                 mov     dword ptr [rbp+HandlerType.Data4], 4A66F9Ah
.text:0000000000001629                 mov     dword ptr [rbp+HandlerType.Data4+4], 55D8FE9Ah

The pseudocode for this handler is shown below:

EFI_STATUS __fastcall SmiHandler_19A0(
        EFI_HANDLE DispatchHandle,
        const void *Context,
        void *CommBuffer,
        UINTN *CommBufferSize)
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND]

  ...
  // size not validated, we can allocate small buffer, then write out of bounds
  CommBufferCopy = (unsigned __int64 *)GetCopy(*CommBufferSize, CommBuffer);
  if ( CommBufferCopy )
  {
    ...
    *((_QWORD *)CommBufferCopy + 2) = Status;     // OOB write
    CopyMemS(CommBuffer, *CommBufferSize, CommBufferCopy, *CommBufferSize);
    Clear(&CommBufferCopy1, *CommBufferSize);
  }
  return 0;
}

GetCopy will allocate a buffer of size *CommBufferSize and copy the contents of the CommBuffer into this buffer:

void *__fastcall GetCopy(UINTN Size, const void *Buffer)
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND]

  result = AllocatePool(Size); // gSmst->SmmAllocatePool wrapper
  if ( result && Size && result != Buffer )
    return CopyMem(result, Buffer, Size);
  return result;
}

It means that CommBufferCopy is a pointer to a buffer on the heap with the size *CommBufferSize. *CommBufferSize not validated in the SMI handler. Thus, if the *CommBufferSize is less than 24, then out-of-bounds write in heap buffer may occur.

To exploit this vulnerability it is enough to:

Set up a Communication Buffer (with MessageSize < 24).
Trigger the SW SMI Handler (SW SMI number and pointer to Communication Buffer are specified in UEFI ACPI table) via 0xB2 IO port.

Disclosure timeline

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

Disclosure Activity	Date
HP PSIRT is notified	2021-07-12
HP PSIRT confirmed reported issue	2021-08-09
HP PSIRT assigned CVE number	2021-08-19
CERT/CC created a case	2021-11-16
HP PSIRT provide patch release	2022-03-08
BINARLY public disclosure date	2022-03-08

Acknowledgements

BINARLY efiXplorer team

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Book a live tour to watch Binarly validate SBOM/CBOM, surface exploitable risks with reachability and exploitation maturity scoring, and chart a measurable path to post-quantum readiness.

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BRLY-2021-038

The heap buffer overflow vulnerability in child SW SMI handler on multiple HP devices.

Public Disclosure Date: Mar 8, 2022

CVE ID

CVE-2022-23930

Vendors Affected

Products Affected

[Device](https://support.hp.com/us-en/drivers/selfservice/hp-prodesk-405-g6-small-form-factor-pc/38230306) / firmware version: `02.05.01 Rev.A`

Summary

BINARLY efiXplorer team has discovered a heap buffer overflow vulnerability in the child SW SMI handler on multiple HP devices that allows heap data corruption.

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Book a live tour to watch Binarly validate SBOM/CBOM, surface exploitable risks, and chart a path to post-quantum readiness.

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Potential Impact

Vulnerability Information

BINARLY internal vulnerability identifier: BRLY-2021-038
HP PSIRT assigned CVE identifier: CVE-2022-23930
CERT/CC assigned case number: VU#683814
CVSS v3.1 8.2 High AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Table of Contents

01.Affected HP firmware

02.Vulnerability description

03.Disclosure timeline

04.Acknowledgements

Affected HP firmware

Device/Firmware	File Name	SHA256 (File PE32 section)	File GUID
Device / firmware version: `02.05.01 Rev.A`	0193	40b09ebb66f7bf702edaaccb08a3f4a5ae96d1f08e1b14cb33b9341d6539fee2	12D06948-6569-42C9-ABA3-E12BACE7B234

Vulnerability description

The vulnerability exists in child the SW SMI handler registered with GUID 4dd19464-68d5-4c6d-9a6f-a6049afed855 and located at offset 0x19A0 in the driver.

It should be noted, that the HandlerType is a stack variable in this case:

.text:000000000000160D                 mov     [rbp+HandlerType.Data1], 4DD19464h
.text:0000000000001614                 ...
.text:000000000000161B                 mov     dword ptr [rbp+HandlerType.Data2], 4C6D68D5h
.text:0000000000001622                 mov     dword ptr [rbp+HandlerType.Data4], 4A66F9Ah
.text:0000000000001629                 mov     dword ptr [rbp+HandlerType.Data4+4], 55D8FE9Ah

The pseudocode for this handler is shown below:

EFI_STATUS __fastcall SmiHandler_19A0(
        EFI_HANDLE DispatchHandle,
        const void *Context,
        void *CommBuffer,
        UINTN *CommBufferSize)
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND]

  ...
  // size not validated, we can allocate small buffer, then write out of bounds
  CommBufferCopy = (unsigned __int64 *)GetCopy(*CommBufferSize, CommBuffer);
  if ( CommBufferCopy )
  {
    ...
    *((_QWORD *)CommBufferCopy + 2) = Status;     // OOB write
    CopyMemS(CommBuffer, *CommBufferSize, CommBufferCopy, *CommBufferSize);
    Clear(&CommBufferCopy1, *CommBufferSize);
  }
  return 0;
}

GetCopy will allocate a buffer of size *CommBufferSize and copy the contents of the CommBuffer into this buffer:

void *__fastcall GetCopy(UINTN Size, const void *Buffer)
{
  // [COLLAPSED LOCAL DECLARATIONS. PRESS KEYPAD CTRL-"+" TO EXPAND]

  result = AllocatePool(Size); // gSmst->SmmAllocatePool wrapper
  if ( result && Size && result != Buffer )
    return CopyMem(result, Buffer, Size);
  return result;
}

To exploit this vulnerability it is enough to:

Set up a Communication Buffer (with MessageSize < 24).
Trigger the SW SMI Handler (SW SMI number and pointer to Communication Buffer are specified in UEFI ACPI table) via 0xB2 IO port.

Disclosure timeline

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

Disclosure Activity	Date
HP PSIRT is notified	2021-07-12
HP PSIRT confirmed reported issue	2021-08-09
HP PSIRT assigned CVE number	2021-08-19
CERT/CC created a case	2021-11-16
HP PSIRT provide patch release	2022-03-08
BINARLY public disclosure date	2022-03-08

Acknowledgements

BINARLY efiXplorer team

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Book a live tour to watch Binarly validate SBOM/CBOM, surface exploitable risks with reachability and exploitation maturity scoring, and chart a measurable path to post-quantum readiness.

Book a Demo

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Potential Impact

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Vulnerability Information

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Affected HP firmware

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Vulnerability description

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Disclosure timeline

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Acknowledgements

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Get started today, Ship and Buy Software You Can Prove Is Safe

Get started today, Ship and Buy Software You Can Prove Is Safe

Potential Impact

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Vulnerability Information

Image preview

Affected HP firmware

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Vulnerability description

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Disclosure timeline

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Acknowledgements

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Get started today, Ship and Buy Software You Can Prove Is Safe