Memory Corruption vulnerability in DXE driver.
BINARLY efiXplorer team has discovered an OOB Write vulnerability in the RLE8 decode routine during BMP file processing in Insyde firmware.
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Potential Impact
An attacker with local access can exploit this vulnerability to elevate privileges from ring 3 or ring 0 (depends on the operating system) to a DXE driver and execute arbitrary code. Malicious code installed as a result of this exploitation could survive operating system (OS) boot process and runtime, or modify NVRAM area on the SPI flash storage (to gain persistence). Additionally, threat actors could use this vulnerability to bypass OS security mechanisms (modify privileged memory or runtime variables), influence OS boot process, and in some cases allow an attacker to hook or modify EFI Runtime services.
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Vulnerability Information
- BINARLY internal vulnerability identifier: BRLY-LOGOFAIL-2023-002
- Insyde PSIRT assigned CVE identifier: CVE-2023-40238
- CVSS v3.1: 8.2 High AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
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Affected modules
| Module name | Module GUID | Module SHA256 |
|---|---|---|
BmpDecoderDxe | a9f634a5-29f1-4456-a9d5-6e24b88bdb65 | 02034e3bdc02ef843651611c1f97f8f2a1deb0be78f9085ac40077eba4260128 |
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Vulnerability description
The pseudocode of the vulnerable function is shown below:
__int64 __fastcall DecodeRLE8(
EFI_GRAPHICS_OUTPUT_BLT_PIXEL *BltOutput,
unsigned __int8 *a2,
__int64 a3,
BMP_IMAGE *Image)
{
unsigned __int64 PixelHeight; // rax
char v5; // r15
unsigned __int64 i; // r11
__int64 PixelWidth; // rbx
unsigned __int64 v11; // r9
char v12; // bp
EFI_GRAPHICS_OUTPUT_BLT_PIXEL *BltEntry; // r8
__int64 v14; // rax
unsigned __int8 *v15; // rsi
__int64 v16; // r10
__int64 v17; // rcx
char v18; // si
__int64 v19; // rax
PixelHeight = Image->BmpHeader.PixelHeight;
v5 = 0;
for ( i = 0i64; i <= PixelHeight; ++i )
{
if ( v5 )
break;
PixelWidth = Image->BmpHeader.PixelWidth;
v11 = 0i64;
v12 = 0;
// BRLY-LOGOFAIL-2023-002
BltEntry = &BltOutput[PixelWidth * (PixelHeight - i - 1)];
do
{
if ( v12 )
break;
v14 = *a2;
v15 = a2 + 1;
v16 = a2[1];
a2 += 2;
if ( (_BYTE)v14 )
{
v17 = (unsigned int)v14;
v11 += v14;
do
{
BltEntry->Red = *(_BYTE *)(a3 + 4 * v16 + 2);// arbitrary write
BltEntry->Green = *(_BYTE *)(a3 + 4 * v16 + 1);// arbitrary write
BltEntry->Blue = *(_BYTE *)(a3 + 4 * v16);// arbitrary write
++BltEntry;
--v17;
}
while ( v17 );
}
else if ( (_BYTE)v16 )
{
if ( (_DWORD)v16 == 1 )
{
v5 = 1;
v12 = 1;
}
else if ( (_DWORD)v16 == 2 )
{
v11 += *a2;
i += v15[2];
a2 = v15 + 3;
BltEntry = &BltOutput[v11 + (unsigned int)PixelWidth * (Image->BmpHeader.PixelHeight - i - 1)];
}
else
{
v11 += v16;
v18 = v16;
do
{
v19 = *a2++;
BltEntry->Red = *(_BYTE *)(a3 + 4 * v19 + 2);
BltEntry->Green = *(_BYTE *)(a3 + 4i64 * (unsigned int)v19 + 1);
BltEntry->Blue = *(_BYTE *)(a3 + 4i64 * (unsigned int)v19);
++BltEntry;
--v16;
}
while ( v16 );
if ( (v18 & 1) != 0 )
++a2;
}
}
else
{
v12 = 1;
}
LODWORD(PixelWidth) = Image->BmpHeader.PixelWidth;
}
while ( v11 <= (unsigned int)PixelWidth );
PixelHeight = Image->BmpHeader.PixelHeight;
}
return 0i64;
}
Where DecodeRLE8 function will be called from the DecodeBMP function:
if ( Image->BmpHeader.CompressionType == 1 )
{
if ( v18 )
sub_330(*a3, v18, 0i64);
DecodeRLE8(v22, v17, &Image->field_36, Image);
return 0i64;
}
}
As we can see from the pseudocode, when BmpHeader->PixelHeight (controllable by the attacker) is equal to 0, BltEntry pointer will be located below BltOutput pointer ((0 - 0 - 1) * BmpHeader->PixelWidth = - BmpHeader->PixelWidth).
Thus, by subsequent write operations, a potential attacker can write data to a controllable address (in the physical memory below BltOutput address).
This vulnerability could lead to the execution of arbitrary code during the DXE phase.
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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 (YYYY-mm-dd) |
|---|---|
Lenovo PSIRT is notified | 2023-06-21 |
Lenovo ID (LEN-132940) is assigned | 2023-06-22 |
CERT/CC is notified | 2023-07-10 |
Insyde PSIRT confirmed reported issues | 2023-09-10 |
Insyde PSIRT assigned CVE ID | 2023-11-27 |
Insyde advisory release date | 2023-12-06 |
BINARLY public disclosure date | 2024-06-19 |
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Acknowledgements
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