DLL Hijacking 2026 — Search Order Abuse, Phantom DLLs & Persistence | Hacking Course Day 40

📰 Originally published on Securityelites — AI Red Team Education — the canonical, fully-updated version of this article.

🔐 ETHICAL HACKING COURSE

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Part of the Ethical Hacking Mastery Course — 100 Days

Day 40 of 100 · 40% complete

⚠️ Authorised Lab Environments Only. DLL hijacking on systems you don’t own or have explicit written permission to test is illegal. All exercises use TryHackMe or your own controlled Windows VM.

Windows applications load DLLs. When a DLL isn’t found at an absolute path, Windows searches a sequence of directories in a defined order. If any of those directories is writable by a low-privilege user before the legitimate DLL location, that user can place a malicious DLL that gets loaded instead of the real one — executing their code in the context of the application loading it. When that application runs as SYSTEM or a higher-privileged account, the malicious DLL runs at that privilege level too. DLL hijacking is the vulnerability that sits under dozens of legitimate Windows applications, waiting for a misconfigured directory permission to become a privilege escalation path.

🎯 What You’ll Master in Day 40

Understand the Windows DLL search order and why it creates vulnerabilities
Identify DLL hijacking opportunities using Process Monitor
Generate a malicious DLL payload with msfvenom
Exploit phantom DLL and DLL search order vulnerabilities
Detect and defend against DLL hijacking as a blue teamer

⏱️ 40 min read · 3 exercises · Day 40 of 100 #### ✅ Before You Start - Day 39 — Scheduled Tasks & Cron — persistence via task scheduler. DLL hijacking is persistence and privilege escalation via a different mechanism: Windows DLL loading behaviour rather than the scheduler. Both survive reboots; DLL hijacking is harder to detect. - Windows lab VM (TryHackMe works) · Kali Linux · Process Monitor (Sysinternals) on Windows · msfvenom ### 📋 Hacking Course Day 40 — DLL Hijacking 1. Windows DLL Search Order 2. Finding DLL Hijacking Opportunities 3. Generating the Malicious DLL 4. Phantom DLLs — Missing DLLs in Privileged Paths 5. Detection and Defence DLL hijacking follows the privilege escalation methodology from Day 39’s scheduled task persistence. The full privilege escalation toolkit is covered in the Privilege Escalation hub. The Kali Linux Commands reference has the full msfvenom DLL generation syntax.

Windows DLL Search Order

When a Windows application calls LoadLibrary(“example.dll”) without a full path, Windows searches directories in a specific order until it finds a matching DLL. The default search order creates the vulnerability: if an attacker can write to any directory that appears in this list before the directory containing the legitimate DLL, their malicious version is loaded first.

WINDOWS DLL SEARCH ORDER (DEFAULT)Copy

Standard DLL search order (SafeDllSearchMode enabled)

1. The directory from which the application was loaded
2. The system directory (C:\Windows\System32)
3. The 16-bit system directory (C:\Windows\System)
4. The Windows directory (C:\Windows)
5. The current working directory (CWD) ← common hijack point
6. Directories in %PATH% environment variable ← another hijack point

Vulnerable conditions (any of these = exploitable)

A) App dir is writable by low-priv user + app runs as SYSTEM/admin
B) DLL does not exist at any path (phantom DLL) + writable dir in search order
C) %PATH% contains a writable directory before legitimate DLL location
D) App runs from a writable CWD (installer staging directories)

Check writable directories in PATH

foreach ($dir in $env:PATH.Split(‘;’)) { if (Test-Path $dir) { (Get-Acl $dir).Access | where {$.IdentityReference -like “Users” -and $.FileSystemRights -match “Write”} | select -First 1 | % { Write-Host “$dir — WRITABLE” } } }

Finding DLL Hijacking Opportunities

Process Monitor is my primary discovery tool on Windows. Filtered to show “NAME NOT FOUND” DLL load attempts from privileged processes, it surfaces every phantom DLL — a DLL that an application tries to load but doesn’t exist anywhere in the search path. Each phantom DLL in a writable directory is a direct hijack opportunity.

PROCESS MONITOR — DLL HIJACK DISCOVERYCopy

Process Monitor filter setup (Sysinternals ProcMon)

Filter → Add: Operation is CreateFile → Include
Filter → Add: Result is NAME NOT FOUND → Include
Filter → Add: Path ends with .dll → Include
Filter → Add: Process name is [target app] → Include

Look for: high-privilege process + writable path + NAME NOT FOUND

Example output:
VulnApp.exe CreateFile C:\Users\Public\version.dll NAME NOT FOUND
VulnApp.exe CreateFile C:\Program Files\App\helper.dll NAME NOT FOUND

Check if the PATH directory is writable

icacls “C:\Users\Public\” | findstr /i “users|everyone|authenticated”
BUILTIN\Users:(W) or (M) = writable = exploitable

PowerShell: find writable directories in system PATH

$env:PATH.Split(‘;’) | ForEach-Object { try { [io.file]::OpenWrite(“$\test.tmp”).close(); Write-Host “$ — WRITABLE”; Remove-Item “$_\test.tmp” } catch {} }

🧠 EXERCISE 1 — THINK LIKE A HACKER (15 MIN)
Design a DLL Hijack Detection Checklist

⏱️ 15 minutes · No tools required

Understanding what to look for before opening Process Monitor saves hours in real engagements. Build the checklist I run on every Windows privilege escalation assessment.

SCENARIO: You have low-privilege access to a Windows 10 workstation.

You need to escalate to SYSTEM or local admin.

BUILD YOUR DLL HIJACKING CHECKLIST:

1. PRIVILEGED PROCESSES Which Windows services run as SYSTEM by default? How do you list them: sc query type=all state=all | ? Why does a SYSTEM process loading a DLL from a writable dir = privilege esc?

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