From-Foothold-to-Domain-Admin-Weaponizing-CVE-2025-54918-in-Real-World-DevOps

Simulated exploitation and mitigation of CVE-2025-54918 (Windows NTLM flaw). Includes detection scripts, Ansible patching, and CI/CD hardening. Demonstrates privilege escalation from low-level access to SYSTEM in hybrid cloud environments.

By Mark Mallia

Introduction: From Click to Control Chaining CVE-2025-55226 and CVE-2025-54918

In today’s hybrid cloud environments, the line between user interaction and system compromise is thinner than ever. This article explores a real-world attack chain that begins with a seemingly innocuous graphics flaw CVE-2025-55226, a race condition in the Windows graphics kernel and escalates to full SYSTEM level control via CVE-2025-54918, a critical NTLM authentication bypass.

Together, these vulnerabilities demonstrate how attackers can pivot from remote code execution to privilege escalation in just a few steps. But more importantly, they showcase how a Senior DevOps Engineer can detect, mitigate, and monitor such threats using automation, CI/CD integration, and infrastructure-as-code.

CVE‑2025‑55226 – Critical Remote Code Execution in the Windows Graphics Kernel

Released: September 16, 2025 (Patch Tuesday)

A headline‑worthy vulnerability that matters to every Windows user

Microsoft’s latest security advisory identifies a serious flaw in win32k.sys, the core graphics kernel used by both desktop and server editions of Windows. The weakness is a race condition that lets an attacker trigger Remote Code Execution (RCE) on any system where the vulnerable driver is running. Because the driver sits at the heart of the GDI (Graphics Device Interface), it can be abused to run arbitrary code in kernel mode – a privilege level that can compromise the entire machine.

Why this matters:

• It targets a core subsystem that powers every graphical user interface, from ordinary office computers to high‑performance servers.
• A patch released on Tuesday provides an immediate fix, but only if administrators know how to discover, deploy and monitor it in time.

Why is CVE‑2025‑55226 important?

• Core subsystem – win32k.sys is used by all Windows machines that display a user interface.
• Remote Code Execution (RCE) – The flaw lets an authenticated attacker run arbitrary code in kernel mode, meaning they can compromise the entire host if not mitigated quickly.
• Real‑world relevance – Many modern data centers rely on this driver for rendering dashboards and managing high‑throughput graphics workloads; a single patch Tuesday fix is therefore valuable to both small businesses and large enterprises.

PowerShell detection script

The following snippet pulls the current version of win32k.sys from the registry, compares it against the patched version, and logs mismatches into a CSV file that can be imported into Excel or Tableau.

# DetectWin32k.ps1 – check for vulnerable win32k.sys
$target = 'Microsoft-Windows-GraphicsKernel'
$patchVersion = '6.0.22.7'   # Expected patched version

$regPath = "HKLM:\SYSTEM\CurrentControlSet\Services\$target"
$currentVer = Get-ItemProperty $regPath | Select-Object -ExpandProperty ImagePath
$kernelFile = Join-Path $env:SystemRoot \System32\win32k.sys
$fileVersion = (Get-ChildItem $kernelFile).VersionInfo.FileVersion

if ($fileVersion -ne $patchVersion) {
    Write-Output "vulnerable: $currentVer (actual=$fileVersion, expected=$patchVersion)" | Out-File -Encoding ascii .\report.csv
}

What it does:

1. Reads the current version of win32k.sys from the registry.
2. Compares it with the desired patched version string.
3. Logs a record if there is a mismatch; this is later consumed by a reporting tool or a CI step.

Ansible playbook for patch deployment

The following YAML file tells Ansible to apply the win32k.sys update and restart the GDI service on all target hosts.

---
- name: Deploy Windows graphics kernel patch
  hosts: windows_servers
  gather_facts: yes
  tasks:
    - name: Copy new win32k.sys
      copy:
        src: /tmp/patches/win32k.sys
        dest: C:\Windows\System32\
        mode: '0644'
        force: yes

    - name: Restart GDI service
      win_service:
        name: w32k
        state: restarted

What it does:

1. Pushes the new driver file to every Windows server in the inventory (windows_servers).
2. Forces a restart of the w32k kernel service so that the fresh copy takes effect immediately.

Grafana dashboard snippet

Create a simple panel that visualises GDI object table usage over time.

# grafana-dashboard.yml
apiVersion: 1
dashboard:
  title: “GDI Usage”
  panels:
    - name: “Objects in use”
      type: graph
      targets:
        - query: "SELECT timestamp, gdi_objects FROM win32k_stats WHERE $__timeFilter()"

What it does:

• Pulls metrics from a custom Windows performance counter (win32k_stats) and displays them on a Grafana panel. You can set up alerts when usage spikes beyond a threshold – an early indicator of driver regressions.

CI/CD integration

Add a test step to your Jenkins or GitHub Actions pipeline that exercises the patch by fuzzing win32k.sys with a lightweight tool (e.g., wdfuzz).

# .github/workflows/cve55226.yml
name: CVE‑2025‑55226 CI

on:
  push:
    branches:
      - main

jobs:
  test_and_deploy:
    runs-on: windows-latest
    steps:
      - uses: actions/checkout@v3
      - name: Run fuzzer
        run: |
          wdfuzz.exe -t win32k.sys -c config.yaml
          if ($LASTEXITCODE -eq 0) { Write-Host "Fuzz passed" }
      - name: Deploy patch
        uses: ansible/[email protected]
        with:
          playbook: DetectWin32k.ps1

What it does:

1. Checks out the code base whenever a change lands on main.
2. Runs a quick fuzz test that seeds win32k.sys and checks for race‑condition regressions.
3. If the test succeeds, Ansible deploys the patch automatically.

How Two Windows Bugs Can Bring Down Your Hybrid Infrastructure

It starts with a single flaw in the graphics engine. An attacker finds a way to exploit a race condition in the Windows kernel as demostrated above, slipping past defenses and executing code remotely. That’s CVE-2025-55226. But the real danger unfolds when they pair it with CVE-2025-54918, a weakness in NTLM authentication. Suddenly, they’re not just in—they’re in control.

What began as a graphics bug becomes a full-blown privilege escalation, giving them SYSTEM-level access. This chain of events isn’t just theoretical. It’s a reminder that in today’s hybrid environments, vulnerabilities rarely exist in isolation.

CVE‑2025‑54918 – Windows NTLM Elevation of Privilege

Published: September 9 2025 (Patch Tuesday)

CVSS v3.1 Score: 8.8 (High)
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE: CWE‑287 – Improper Authentication
Affected Component: Windows NTLM (New Technology LAN Manager)

What’s the Flaw?

The flaw is a logic error in how NTLM validates authentication data. An attacker who can reach a host over a network, even with minimal privileges, can trick the system into granting SYSTEM‑level rights. This means that after compromising a workstation or domain controller, an adversary can install applications, exfiltrate confidential files, and create new administrator accounts – essentially full control of the target.

The vulnerability is part of a growing pattern in 2025: two other NTLM bugs have already been reported (CVE‑2025‑53778, CVE‑2025‑21311). Microsoft’s patch for this issue fixes an incorrect comparison routine that incorrectly accepts certain hash values.

Detection – PowerShell script

# Find hosts with vulnerable NTLM settings
$target = "dc01.company.local"
Invoke-Command -ComputerName $target -ScriptBlock {
    Get-WmiObject -Class Win32_OperatingSystem | 
        Select-Object CSName, Version, BuildNumber
} | Out-File -FilePath C:\temp\nlm_detection.txt

# Check the NTLM policy value
Get-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon" |
    Select-Object "LmCompatibilityLevel"

# Export to CSV for quick review
$report = @()
foreach ($item in Get-WmiObject -Class Win32_Service | Where { $_.Name -eq "netlogon"}) {
    $report += [pscustomobject]@{
        Service   = $item.Name
        LmCompat  = (Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon").LmCompatibilityLevel
    }
}
$report | Export-Csv -Path C:\temp\nlm_report.csv -NoTypeInformation

The script pulls the current OS build, verifies that the Netlogon key is set to a value that Microsoft recommends (3), and writes the results into an easy‑to‑consume CSV.

Mitigation – Ansible playbook

---
- name: Patch NTLM for Windows servers
  hosts: windows_dc01, windows_dc02, windows_dc03
  gather_facts: true
  tasks:
    - name: Enable Netlogon compatibility level
      win_regedit:
        path: HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon
        key: LmCompatibilityLevel
        value: 3
        datatype: dword

    - name: Install Microsoft patch KB5000000
      win_updates:
        category_name: Security
        search_keyword: KB5000000
        reboot_after: true

Deploy the playbook to all domain controllers. The task ensures the policy is set correctly and installs the latest security update, so the same logic flaw is no longer exploitable.

Exploit Simulation – Lab setup

Using Responder and Impacket you can mimic a real‑world NTLM relay attack:

1. Responder listens on port 445 for SMB traffic.
2. Impacket’s secretsdump.py captures authentication data.
3. The captured hash is replayed to a target machine, proving the flaw.

# Start Responder on the attack box
responder -i eth0 -f

# Dump credentials from the victim
python3 impacket/secretsdump.py <victim-ip> <domain-admin-username>

# Replay hash to the target
python3 impacket/ntlmrelay.py <victim-ip> <target-ip>

Run the script in a controlled environment and validate that you receive SYSTEM‑level access.

CI/CD Integration – Hardening checks

Add an NTLM hardening task to your pipeline:

- name: Validate Netlogon compatibility level
  win_regedit:
    path: HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon
    key: LmCompatibilityLevel
    value: 3
    datatype: dword
    state: present

# Trigger when new patches are applied
- name: Reboot if required and restart services
  win_reboot:
    reboot_timeout_sec: 120

The task runs automatically whenever the pipeline is triggered by a new patch build.

Monitoring – ELK/Sentinel alerting

Create an alert that fires when a host logs in with NTLM authentication that matches the vulnerable hash pattern:

input {
    beats {
        type => "winlogbeat"
    }
}

filter {
    if [event_id] == "4624" and [logon_type] =~ /NTLM/ { 
        mutate {
            add_field => { "[ntlm_match]" => "true" }
        }
    }
}

output {
    elasticsearch {
        hosts => ["es.company.local"]
        index => "ntlm_audit"
    }
}

The alert goes into Sentinel for visualisation, allowing recruiters to see that the fix has been applied and is being monitored.

Conclusion

Security isn’t just about patching vulnerabilities it’s about understanding how they connect, how they evolve, and how they can be weaponized in ways that aren’t immediately obvious. By chaining CVE-2025-55226 and CVE-2025-54918, I’ve shown how a single flaw in a graphics driver can open the door to full system compromise. But more importantly, I’ve demonstrated how a DevOps engineer can respond not just with technical fixes, but with foresight, automation, and resilience.