Performing Privilege Escalation On Linux

Performing Privilege Escalation on Linux

Legal Notice: This skill is for authorized security testing and educational purposes only. Unauthorized use against systems you do not own or have written permission to test is illegal and may violate computer fraud laws.

Overview

Linux privilege escalation involves elevating from a low-privilege user account to root access on a compromised system. Red teams exploit misconfigurations, vulnerable services, kernel exploits, and weak permissions to achieve root. This skill covers both manual enumeration techniques and automated tools for identifying and exploiting privilege escalation vectors.

When to Use

• When conducting security assessments that involve performing privilege escalation on linux
• When following incident response procedures for related security events
• When performing scheduled security testing or auditing activities
• When validating security controls through hands-on testing

Most Often Missed & How to Confirm

• Run the full enumerator, then verify by hand: linpeas.sh/LinEnum.sh and pspy (for cron/processes) — the high-signal vectors are easy to skip in the noise.
• Check every vector: SUID/SGID (find / -perm -4000 2>/dev/null), sudo -l + GTFOBins, Linux capabilities (getcap -r / 2>/dev/null), writable cron/systemd units, writable $PATH/service binaries, NFS no_root_squash, and kernel exploits (match uname -r to known CVEs as a last resort).
• Credentials lying around: .bash_history, config/.env files, SSH keys, world-readable backups, DB creds.
• Confirm a hit: id returns uid=0(root) (or you can read /etc/shadow). Don't conclude "no privesc" until SUID, sudo, capabilities, cron, services, and writable paths are all checked — and re-run enumeration after every new credential found.

Prerequisites

• Familiarity with red teaming concepts and tools
• Access to a test or lab environment for safe execution
• Python 3.8+ with required dependencies installed
• Appropriate authorization for any testing activities

MITRE ATT&CK Mapping

• T1548.001 - Abuse Elevation Control Mechanism: Setuid and Setgid
• T1548.003 - Abuse Elevation Control Mechanism: Sudo and Sudo Caching
• T1068 - Exploitation for Privilege Escalation
• T1574.006 - Hijack Execution Flow: Dynamic Linker Hijacking
• T1053.003 - Scheduled Task/Job: Cron
• T1543.002 - Create or Modify System Process: Systemd Service

Key Escalation Vectors

SUID/SGID Binaries

• Find SUID binaries: find / -perm -4000 -type f 2>/dev/null
• Check GTFOBins for exploitation methods
• Custom SUID binaries may have vulnerabilities

Sudo Misconfigurations

• sudo -l to list allowed commands
• Wildcards in sudo rules allow injection
• NOPASSWD entries for dangerous commands
• sudo versions vulnerable to CVE-2021-3156 (Baron Samedit)

Kernel Exploits

• Dirty Cow (CVE-2016-5195) for older kernels
• Dirty Pipe (CVE-2022-0847) for kernel 5.8+
• PwnKit (CVE-2021-4034) for pkexec
• GameOver(lay) (CVE-2023-2640, CVE-2023-32629) for Ubuntu

Cron Job Abuse

• World-writable cron scripts
• PATH hijacking in cron jobs
• Wildcard injection in cron commands

Capabilities

• getcap -r / 2>/dev/null to find binaries with capabilities
• cap_setuid allows UID manipulation
• cap_dac_override bypasses file permissions

Writable Service Files

• Systemd unit files with weak permissions
• Init scripts writable by non-root users
• Socket files in accessible locations

Tools and Resources

Validation Criteria

• Enumeration performed using automated tools
• Privilege escalation vector identified
• Root access achieved through identified vector
• Evidence documented (screenshots, command output)
• Alternative escalation paths identified