.webp)
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.
Binarly REsearch Team has discovered a multiple OOB Read/Write vulnerabilities in Insyde firmware related to lack of validation in the LZW decoder routine in the GifDecoderDxe module.
An attacker with local access can exploit this vulnerability to elevate privileges from ring 3 or ring 0 (depending 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.
The pseudocode of the vulnerable function is shown below:
__int64 __fastcall DecodeLZW(
char *Image,
unsigned __int64 a2,
char a3,
__int64 a4,
unsigned __int16 a5,
unsigned __int16 a6,
__int64 a7)
{
HeapStruct *v7; // r13
char Value; // cl
char *v10; // r11
unsigned __int16 Bound; // bx
unsigned __int8 v12; // r9
__int16 v13; // di
unsigned __int16 v14; // r12
unsigned __int8 v15; // si
unsigned int v16; // r10d
unsigned __int16 v17; // r15
unsigned __int16 v18; // r8
unsigned __int16 Index; // cx
HeapStruct *HeapArrayEntry; // rax
unsigned __int16 v21; // bp
_BYTE *v22; // r14
unsigned __int64 v23; // rax
char v24; // cl
unsigned __int16 v25; // r11
__int16 v26; // r9
unsigned __int16 v27; // ax
unsigned __int16 v28; // ax
__int64 v29; // rdx
__int64 v30; // rax
__int64 v31; // rdx
char v33; // [rsp+0h] [rbp-68h]
unsigned __int8 v34; // [rsp+1h] [rbp-67h]
unsigned __int16 v35; // [rsp+2h] [rbp-66h]
__int16 v36; // [rsp+4h] [rbp-64h]
__int16 v37; // [rsp+6h] [rbp-62h]
unsigned __int16 v38; // [rsp+8h] [rbp-60h]
unsigned __int16 v39; // [rsp+10h] [rbp-58h]
char *v40; // [rsp+70h] [rbp+8h]
v7 = HeapArray;
Value = *Image;
v10 = Image + 1;
Bound = 1 << Value;
v40 = v10;
v39 = Bound;
v12 = Value + 1;
v36 = -1;
v37 = (1 << Value) + 1;
v13 = -1;
v34 = Value + 1;
v38 = (1 << Value) + 2;
v14 = v38;
v35 = v38;
v15 = Value + 1;
v33 = Value + 1;
v16 = 0;
v17 = 0;
v18 = 0;
Index = 0;
if ( Bound )
{
HeapArrayEntry = HeapArray;
// BRLY-LOGOFAIL-2023-004
do
{
HeapArrayEntry->field_2 = Index++;
HeapArrayEntry->field_0 = -1;
HeapArrayEntry = (HeapArrayEntry + 4);
}
while ( Index < Bound );
v7 = HeapArray;
}
if ( v12 >> 3 <= a2 )
{
v21 = a6;
v22 = qword_1D50;
do
{
v23 = v16 >> 3;
v24 = v16 & 7;
v16 += v15;
v25 = ((1 << v15) - 1) & (*&v10[v23] >> v24);
if ( v25 == v37 )
return v16;
if ( v25 == Bound )
{
v14 = v38;
v15 = v12;
v35 = v38;
v13 = Bound;
v33 = v12;
v36 = Bound;
goto LABEL_40;
}
if ( v18 == v21 )
return v16;
v26 = -1;
if ( v25 >= v14 )
{
if ( v13 == Bound )
goto LABEL_44;
v26 = 0;
v28 = v13;
if ( v13 != -1 )
{
do
{
v22[++v26] = *(&v7->field_2 + 4 * v28);
v28 = *(&v7->field_0 + 2 * v28);
}
while ( v28 != 0xFFFF );
v15 = v33;
v21 = a6;
}
*v22 = v22[v26];
}
else
{
v27 = v25;
if ( v25 != 0xFFFF )
{
do
{
v22[++v26] = *(&v7->field_2 + 4 * v27);
v27 = *(&v7->field_0 + 2 * v27);
}
while ( v27 != 0xFFFF );
v21 = a6;
}
if ( v13 == Bound )
goto LABEL_23;
}
v29 = v14++;
v35 = v14;
*(&v7->field_0 + 2 * v29) = v13;
*(&v7->field_2 + 4 * v29) = v22[v26];
LABEL_23:
if ( v26 >= 0 )
{
do
{
v30 = v26--;
v31 = v22[v30];
LODWORD(v30) = v17++;
*(a7 + 4i64 * (v30 + a5 * v18)) = *(a4 + 4 * v31);
if ( v17 == a5 )
{
if ( a3 )
{
if ( (v18 & 7) != 0 )
{
if ( (v18 & 3) != 0 )
{
if ( (v18 & 1) != 0 )
{
v18 += 2;
}
else
{
v18 += 4;
if ( v18 >= v21 )
v18 = 1;
}
}
else
{
v18 += 8;
if ( v18 >= v21 )
v18 = 2;
}
}
else
{
v18 += 8;
if ( v18 >= v21 )
v18 = 4;
}
}
else
{
++v18;
}
v17 = 0;
if ( v18 == v21 )
break;
}
}
while ( v26 >= 0 );
Bound = v39;
v13 = v36;
v15 = v33;
v14 = v35;
v7 = HeapArray;
}
LABEL_40:
if ( v14 < 1 << v15 )
goto LABEL_43;
if ( v15 < 0xCu )
{
v33 = ++v15;
LABEL_43:
v13 = v25;
v36 = v25;
}
LABEL_44:
v12 = v34;
v10 = v40;
}
while ( (v16 + v15) >> 3 <= a2 );
}
return v16;
}As we can see from the pseudocode:
Value is controllable and may take values from 0x00 to 0xff Value = 15, Bound will take max value ( 32768) HeapArray have 4096 elements, so heap overflow will happen here: HeapArrayEntry = HeapArray;
do
{
// Vulnerability OOB Write here
HeapArrayEntry->field_2 = Index++;
HeapArrayEntry->field_0 = -1;
HeapArrayEntry = (HeapArrayEntry + 4);
}
while ( Index < Bound );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.
Binarly REsearch Team
.svg)
