Memory contents leak / information disclosure vulnerability in DXE driver on Dell platform.
BINARLY efiXplorer team has discovered a memory contents leak / information disclosure vulnerability that allows a potential attacker to dump stack memory or global memory into an NVRAM variable. This in turn could help building a successful attack vector based on exploiting a memory corruption vulnerability.
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Potential Impact
An attacker with high physical access can exploit this vulnerability to read the contents of stack memory or global memory. This information could help with exploitation of other vulnerabilities in DXE 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-2022-159
- Dell PSIRT assigned CVE identifier: CVE-2023-28060
- DSA identifier: DSA-2023-099/DSA-2023-204
- CVSS v3.1: 4.9 Medium AV:P/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
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Affected Dell firmware
| Product | Firmware version | CPU | Module name | Module GUID | Module SHA256 |
|---|---|---|---|---|---|
Latitude 3120 | 0.1.13.1 | AMD | 9BCEDB6D-13CA-473E-B605-8A47688729FA | 9bcedb6d-13ca-473e-b605-8a47688729fa | adc756cd7143c8c1ec9e1f776aa1c7cee49da09f6e02b5bc609bc6969d977dcb |
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Vulnerability description
Let's take Latitude 3120's firmware (version: 0.1.13.1, module sha256: adc756cd7143c8c1ec9e1f776aa1c7cee49da09f6e02b5bc609bc6969d977dcb) as an example.
The following code in the module actually allows leaking memory:
- a call to a
gRT->GetVariable()offset:0xa65 - a call to a
gRT->SetVariable()offset:0xa9c
EFI_STATUS __fastcall sub_8AC()
{
EFI_GUID VendorGuid; // [rsp+30h] [rbp-D0h] BYREF
EFI_GUID v2; // [rsp+40h] [rbp-C0h] BYREF
EFI_GUID v3; // [rsp+50h] [rbp-B0h] BYREF
char Data[226]; // [rsp+60h] [rbp-A0h] BYREF
__int16 v5; // [rsp+142h] [rbp+42h]
int v6[2]; // [rsp+300h] [rbp+200h] BYREF
char v7; // [rsp+30Ah] [rbp+20Ah]
char v8; // [rsp+930h] [rbp+830h]
UINT32 Attributes; // [rsp+A90h] [rbp+990h] BYREF
char v10; // [rsp+A98h] [rbp+998h] BYREF
int v11; // [rsp+A99h] [rbp+999h]
__int16 v12; // [rsp+A9Dh] [rbp+99Dh]
UINTN DataSize; // [rsp+AA0h] [rbp+9A0h] BYREF
VendorGuid.Data1 = -1332766721;
*&VendorGuid.Data2 = 1100211944;
*VendorGuid.Data4 = -1637967959;
*&VendorGuid.Data4[4] = 853215899;
v2.Data1 = 1165015025;
*&v2.Data2 = 1229172200;
*v2.Data4 = 1681965965;
*&v2.Data4[4] = -2078047118;
v3.Data1 = -1426528487;
*&v3.Data2 = 1083787512;
*v3.Data4 = 1600452518;
*&v3.Data4[4] = 1028417981;
sub_1130(v6, 0, 0x77Fui64);
v10 = 0;
v11 = 0;
v12 = 0;
DataSize = 667i64;
gRT->GetVariable(L"CpuSetup", &VendorGuid, &Attributes, &DataSize, Data);
v5 = 256;
gRT->SetVariable(L"CpuSetup", &VendorGuid, Attributes, DataSize, Data);
DataSize = 1919i64;
gRT->GetVariable(L"PchSetup", &v2, &Attributes, &DataSize, v6);
v8 = 0;
v7 = 0;
gRT->SetVariable(L"PchSetup", &v2, Attributes, DataSize, v6);
DataSize = 7i64;
gRT->GetVariable(L"SiSetup", &v3, &Attributes, &DataSize, &v10);
LOBYTE(v11) = 0;
return gRT->SetVariable(L"SiSetup", &v3, Attributes, DataSize, &v10);
}
The gRT->SetVariable() service is called with the DataSize as an argument, which will be overwritten inside the gRT->GetVariable() service if the length of SiSetup NVRAM variable is greater than 7.
Thus, a potential attacker can dump X - 7 bytes from the stack (or global memory) into SiSetup NVRAM variable by setting SiSetup NVRAM variable's size to X > 7.
To fix this vulnerability the DataSize must be re-initialized with the size of SiSetup before calling gRT->SetVariable().
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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) |
|---|---|
Dell PSIRT is notified | 2022-12-29 |
Dell PSIRT confirmed reported issue | 2023-03-16 |
Dell PSIRT assigned CVE number | 2023-06-15 |
Dell PSIRT provide patch release | 2023-06-15 |
BINARLY public disclosure date | 2023-06-21 |
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Acknowledgements
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