CVE-2026-2703 | xlnt-community xlnt up to 1.6.1 Encrypted XLSX File Parser base64.cpp decode_base64 off-by-one (Issue 137)

<#
.SYNOPSIS
    iShareStuff CTI Fleet Remediation Automation for CVE-2026-2703
.DESCRIPTION
    Applies security updates and checks winget/PSWindowsUpdate for patch resolution.
    Target: xlnt-community | Generated: 2026-09-25 07:23:21 UTC
#>

#Requires -RunAsAdministrator
[CmdletBinding()]
param(
    [switch]$DryRun = $false
)

Write-Host "[+] Initiating Fleet Security Patch for CVE-2026-2703..." -ForegroundColor Cyan

# 1. Check & Install PSWindowsUpdate if absent
if (-not (Get-Module -ListAvailable -Name PSWindowsUpdate)) {
    Write-Host "[*] Registering PSWindowsUpdate module from PSGallery..." -ForegroundColor Yellow
    [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
    Install-PackageProvider -Name NuGet -MinimumVersion 2.8.5.201 -Force | Out-Null
    Install-Module -Name PSWindowsUpdate -Force -Confirm:$false | Out-Null
}

# 2. Query Windows Update Catalog for applicable Security KBs
Write-Host "[*] Scanning for pending security hotfixes..." -ForegroundColor Gray
Import-Module PSWindowsUpdate -Force

if ($DryRun) {
    Get-WUList -MicrosoftUpdate
    Write-Host "[!] DryRun active: No changes applied." -ForegroundColor Yellow
    exit 0
}

# 3. Apply Security KBs without uncontrolled reboot
try {
    Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot -Verbose
    Write-Host "[✔] Windows Update security rollups successfully deployed." -ForegroundColor Green
} catch {
    Write-Warning "[-] Windows Update failed or returned pending reboot: $_"
}

# 4. Optional Winget Userland Upgrade Check
if (Get-Command winget.exe -ErrorAction SilentlyContinue) {
    Write-Host "[*] Auditing installed software via Winget..." -ForegroundColor Gray
    winget upgrade --all --accept-package-agreements --accept-source-agreements --silent || true
}

Write-Host "[✔] Host remediation audit completed for CVE-2026-2703." -ForegroundColor Green

---
# ==============================================================================
# iShareStuff CTI Multi-OS Fleet Remediation Playbook
# Advisory Reference : CVE-2026-2703
# Target Infrastructure : xlnt-community
# Timestamp : 2026-09-25 07:23:21 UTC
# ==============================================================================
- name: "CTI Remediation Playbook for CVE-2026-2703"
  hosts: all
  become: true
  gather_facts: true

  tasks:
    - name: "Log remediation initiation for CVE-2026-2703"
      ansible.builtin.debug:
        msg: "Executing automated patch mitigation for advisory CVE-2026-2703 on {{ inventory_hostname }}"

    # Debian & Ubuntu Automation
    - name: "Update apt cache and install security updates (Debian/Ubuntu)"
      ansible.builtin.apt:
        upgrade: dist
        update_cache: yes
        autoremove: yes
      when: ansible_os_family == "Debian"

    # RedHat / CentOS / Alma / Rocky Automation
    - name: "Apply all security errata via DNF/YUM (Enterprise Linux)"
      ansible.builtin.dnf:
        name: "*"
        state: latest
        security: yes
      when: ansible_os_family == "RedHat"

    # SUSE Linux Automation
    - name: "Apply security patches via Zypper (SUSE)"
      community.general.zypper:
        type: patch
        category: security
        state: latest
      when: ansible_os_family == "Suse"

    # Windows Fleet Automation
    - name: "Install critical and security Windows Updates"
      ansible.windows.win_updates:
        category_names:
          - SecurityUpdates
          - CriticalUpdates
          - UpdateRollups
        state: installed
      when: ansible_os_family == "Windows"

    - name: "Record audit completion timestamp"
      ansible.builtin.file:
        path: "/var/log/isharestuff_cti_CVE-2026-2703.remediated"
        state: touch
        mode: "0640"
      when: ansible_os_family != "Windows"