Understanding Privilege Escalation: Attacks, Types, and Techniques

Privilege escalation is a critical security threat where attackers exploit system flaws to gain higher levels of access than originally authorized. Whether targeting a single device or an entire cloud infrastructure, such attacks can lead to full system compromise.

In fact, according to IBM’s Cost of a Data Breach Report 2024, compromised credentials and privilege misuse accounted for nearly 20% of breaches, with an average cost of $4.5 million per incident.

In this blog, we’ll break down what privilege escalation is, explore its common types, highlight the vulnerabilities that make it possible, and explain how cybercriminals exploit these weaknesses to breach security defenses.

What is Privilege Escalation?

Privilege escalation is when an attacker gains elevated access to resources usually protected by an application or user. For example, an attacker who gains access to a low-privileged user account on a system may exploit a vulnerability to gain administrator or root-level access.

How does a Privilege Escalation Attack work?

A privilege escalation attack typically involves the following steps:

Initial Access:

The attacker first gains limited access to a system, this could be through a compromised user account, malware, or phishing.

Scanning for Vulnerabilities:

Once inside, they probe the system for misconfigurations, software bugs, or unpatched vulnerabilities that allow privilege escalation (e.g., insecure file permissions, outdated software, kernel exploits).

Exploitation:

The attacker uses these vulnerabilities to elevate their privileges. For example:

• A regular user might gain administrator/root access.
• A guest user might execute commands reserved for privileged users.

Gaining Control:

With elevated privileges, the attacker can:

• Install malicious software
• Access restricted files
• Create backdoors for persistent access
• Exfiltrate sensitive data
• Disable security mechanisms

Covering Tracks:

Skilled attackers often erase logs or use rootkits to hide their actions, making detection harder

What is a Privilege Escalation Vulnerability?

A privilege escalation vulnerability is a type of security weakness that allows an attacker to increase their level of access within a system, often moving from a regular user account to one with administrative or root privileges. These vulnerabilities are typically exploited after an attacker gains initial access to a system, and they serve as a crucial step in gaining deeper control over the target environment.

Types of Privilege Escalation

1. Vertical Privilege Escalation

This occurs when a user with limited privileges gains access to a higher privilege level, such as an admin or root user. For example, a standard user exploits a vulnerability to gain root access in Linux.

• Linux Dirty COW (CVE-2016-5195): Allowed unprivileged users to write to read-only memory, leading to root access.
  
• Windows PrintNightmare (CVE-2021-34527): Enabled remote code execution and privilege escalation via Print Spooler.

2. Horizontal Privilege Escalation

This occurs when a user accesses data or functionality of another user with the same privilege level. Example: A user accessing another user’s private messages or account data without permission.

• Facebook bug (2015): A researcher could view private photos of any user by manipulating a GraphQL query.
  
• Instagram IDOR flaw: Allowed viewing other users’ archived stories by altering media IDs in API calls.

Real-world examples of Privilege Escalation Attack

These examples demonstrate the wide variety of privilege escalation attacks, ranging from OS-level kernel exploits to web application misconfigurations and credential abuse. Each highlights the importance of regular patching, proper access controls, and thorough auditing of system configurations to prevent unauthorized access and system compromise.

1. Dirty COW (CVE-2016-5195) Linux Kernel Exploit

• The Dirty COW vulnerability is one of the most widely known privilege escalation attacks on Linux systems. 
• This vulnerability takes advantage of a race condition in the Linux kernel’s memory management system, specifically the copy-on-write (COW) mechanism. 
• When a process requests a read-only memory mapping, the kernel is supposed to prevent changes to the underlying file. 
• However, the flaw allows an attacker to exploit the timing of memory operations to write to files they shouldn’t have access to.
•  For example, a non-privileged user can modify the /etc/passwd file and replace the root user’s password with one they control. Once the change is made, the attacker can switch to the root account and gain complete administrative control over the system.

This attack is significant because it requires no special privileges and affects many Linux distributions. Later kernel versions patched it, but systems that have not been updated remain vulnerable.

2. PrintNightmare (CVE-2021-34527) Windows Print Spooler Flaw

• PrintNightmare is a critical privilege escalation vulnerability in the Windows Print Spooler service that allows attackers to execute arbitrary code with SYSTEM-level privileges.
• Initially discovered as a remote code execution vulnerability, the flaw was later found to allow even local users to abuse it to escalate their privileges. 
• The attack involves tricking the Print Spooler into loading a malicious DLL from a remote or local location. Because the Print Spooler runs with SYSTEM privileges, any code executed through it inherits the highest level of access on a Windows machine. 
• This vulnerability was particularly dangerous in domain environments where multiple machines shared printer configurations. It allowed attackers to move laterally across networks or completely control servers. 
• Microsoft released emergency patches to address this vulnerability, and many organizations were forced to disable the Print Spooler service as a temporary mitigation.

3. Insecure Direct Object Reference (IDOR) Web Application Misconfiguration

• A horizontal privilege escalation example can be seen in web applications vulnerable to Insecure Direct Object Reference (IDOR). 
• This occurs when an application exposes internal object identifiers (like user IDs or file names) in URLs or APIs without proper authorization checks. 
• For example, an attacker logged in as a regular user might notice their profile is accessed via a URL like https://example.com/user/1001. By changing the ID to 1002, they may access another user’s profile, including sensitive personal information.
• In a real-world case, a security researcher discovered such a vulnerability in an extensive banking application. Changing the account ID in a request allowed access to other users’ transaction histories and balances. 
• This attack doesn’t require admin access and can often be executed through simple browser manipulation, making it highly dangerous if proper access controls are not implemented.

4. Token Impersonation Using Mimikatz: Windows Domain Environment

• Mimikatz is a well-known post-exploitation tool that attackers use to extract credentials and tokens from memory on Windows systems. In domain environments, it is often used for privilege escalation through token impersonation. 
• After compromising a machine, an attacker with local administrator rights can use Mimikatz to dump authentication tokens stored in memory. These tokens can be used to impersonate high-privileged users, such as domain administrators. 
• Once a token is obtained, the attacker can inject it into their session, effectively becoming that user without needing their password. 
• This escalation is particularly stealthy because it doesn’t rely on traditional credential theft; it uses existing sessions. Attackers often combine this technique with tools like Pass-the-Hash or Pass-the-Ticket to move laterally and escalate privileges across the network.

Common Privilege Escalation Techniques

Privilege escalation is a crucial phase in the attack lifecycle where threat actors move from limited access to gaining control over higher-privileged accounts or resources. These techniques are typically categorized based on the platform. Below are the most common techniques used across environments:

1. Exploiting Vulnerable Services or Kernels

Attackers often target unpatched operating system components, services, or kernel-level vulnerabilities. 

For instance, flaws in the Linux kernel (like Dirty COW) or Windows components (like Print Spooler in PrintNightmare) can execute code with SYSTEM or root privileges. Exploiting these bugs allows attackers to bypass standard user restrictions and gain full administrative access.

2. Abusing Misconfigured SUID or Sudo (Linux)

On Linux systems, misconfigured SUID (Set User ID) binaries or sudo permissions can be dangerous. An attacker might find a binary owned by root that runs with elevated privileges. 

If this binary is exploitable, such as by allowing command injection or calling system utilities insecurely, it can be hijacked to spawn a root shell. Similarly, if a user can run specific commands via sudo without proper restrictions, they can often leverage tools like vi, less, or awk to escalate privileges.

3. DLL Hijacking and Unquoted Service Paths (Windows)

In Windows environments, DLL hijacking occurs when an application loads a malicious DLL placed by the attacker instead of a legitimate one. This is possible if the application searches for DLLs in insecure or user-writable locations. 

Similarly, unquoted service paths in Windows services can be exploited when spaces in executable paths are not enclosed in quotation marks. An attacker can insert a malicious binary with a matching name in an earlier part of the path to execute it with SYSTEM privileges when the service starts.

4. Exploiting Weak File or Folder Permissions

Poorly set permissions on sensitive files or folders can be exploited to modify system configurations or binaries. For example, if a regular user has write access to a script that runs as root via a scheduled task or cron job, the attacker can replace the script with malicious code. 

On Windows, modifying service binaries or startup programs due to misconfigured ACLs (Access Control Lists) can also lead to privilege escalation.

5. Scheduled Tasks and Cron Job Abuse

Scheduled tasks and cron jobs are often used to run periodic scripts. If high-privilege users own these jobs but are editable by normal users, attackers can insert malicious payloads that will be executed with elevated rights. 

Similarly, tasks that rely on writable configuration files or scripts offer easy privilege escalation paths when not adequately secured.

6. Token Manipulation and Impersonation (Windows)

In Windows systems, especially domain environments, attackers often use tools like Mimikatz to extract and reuse authentication tokens. 

This allows them to impersonate higher-privileged users without knowing their passwords. Techniques such as Pass-the-Hash and Pass-the-Ticket enable lateral movement and elevation by leveraging stolen credentials or Kerberos tickets.

7. Insecure Application Configuration (Web)

Web applications often suffer from horizontal privilege escalation due to broken access controls. If role validation is missing or weak, a regular user might gain access to administrative functions by changing parameters in the request (e.g., modifying a user ID or elevating their role in a JWT token). 

This vulnerability allows attackers to escalate web interface privileges without system-level access.

8. Exposed Secrets and Credentials

Sensitive data such as passwords, API keys, or SSH credentials sometimes end up in environment variables, configuration files, backup files, or even public Git repositories. 

An attacker who discovers these credentials can use them to authenticate as privileged users or services. Once authenticated, they may be able to perform administrative actions or pivot further within a network.

9. Kernel Module Loading and Driver Abuse

In advanced attacks, if a user can load custom kernel modules or drivers (especially in embedded or misconfigured systems), they can execute code in kernel space. This provides the highest control over the system, bypassing almost all user-space security mechanisms.

10. Abusing Insecure APIs and Inter-Process Communication

Applications that expose insecure APIs or use weak inter-process communication (IPC) mechanisms can often be hijacked to execute commands or read/write data with elevated privileges. Attackers can inject commands or alter responses in poorly secured D-Bus (Linux), RPC (Windows), or socket-based communication channels.

How to Recognize a Privilege Escalation Attack?

Below are the most common indicators that a privilege escalation attack might be taking place:

1. Unusual Account Behavior

One of the most common signs of privilege escalation is when a non-privileged or newly created user account suddenly performs privileged actions. For example, a standard user account attempting to access system files, change configurations, or install software could signal that the account has been compromised or elevated illegitimately. Similarly, service accounts or users with no administrative role performing administrative actions should raise red flags.

2. Multiple Failed Access Attempts

Attackers often probe systems to discover paths to privilege escalation. This may involve repeated failed attempts to access protected files or run privileged commands, followed by a sudden success. This behavior suggests trial-and-error methods or automation tools are being used, such as brute-forcing sudo permissions or exploiting misconfigured binaries.

3. Unauthorized Use of ‘sudo’ or ‘Run as Administrator’

If a user who doesn’t usually use sudo on Linux or “Run as Administrator” on Windows begins to do so, especially for unusual commands or scripts, it could be a sign of privilege escalation. Monitoring command history and access logs can reveal patterns like sudo su, chmod +s, or attempts to access /etc/sudoers.

4. Execution of Privilege Escalation Tools

Attackers often use known tools like Mimikatz, WinPEAS, LinPEAS, PowerUp, or SharpUp to discover and exploit privilege escalation opportunities. The presence or execution of these tools in your environment, especially in temporary directories, PowerShell logs, or user folders, should trigger immediate investigation.

5. Changes to System Binaries or Configuration Files

Unauthorized modifications to sensitive files such as /etc/passwd, /etc/shadow, sudoers, Windows Registry keys, or service configurations could indicate an attacker is trying to create a backdoor or escalate privileges. Attackers might also install malicious scripts or replace binaries in paths used by scheduled tasks or services.

6. New Services or Scheduled Tasks

Attackers may set up scheduled tasks (Windows) or cron jobs (Linux) that run with elevated privileges to maintain persistence. If a new task appears that wasn’t deployed through a known administrative process, it could be part of a privilege escalation or post-exploitation routine.

7. Logon from Unusual Locations or Timeframes

Privileged accounts accessed from unexpected IP addresses, locations, or outside of business hours can indicate that an attacker has successfully escalated privileges and is now using those accounts to take control of the system.

8. Unusual Process Activity

Privilege escalation often involves spawning new shells, executing binaries from unusual paths (e.g., /tmp or %TEMP%), or processes running with elevated permissions that unprivileged users launched. Behavior like a low-level user spawning a root-owned process is abnormal and should be reviewed.

9. Use of Exploit Code or Payloads

If exploit payloads such as buffer overflow code, shellcode, or known privilege escalation scripts are found on the system, especially in temporary or user-writable directories, it likely means someone is attempting or has succeeded in escalating privileges.

10. System Logs and Security Alerts

Modern security tools and operating systems often log activities that can signal privilege escalation attempts. Key log files include:

• Linux: /var/log/auth.log, /var/log/secure, auditd logs
  
• Windows: Security Event Logs (IDs 4672, 4688, 4624 with admin tokens)
  

Security Information and Event Management (SIEM) tools like Splunk, ELK Stack, or Microsoft Sentinel can help correlate events and detect privilege escalation patterns across systems.

How to Protect Yourself from Privilege Escalation Attacks?

Here are the most effective strategies to prevent privilege escalation:

1. Apply the Principle of Least Privilege (PoLP)

• Assign users, applications, and services only the permissions they need.
  
• Use role-based access control (RBAC) to manage permissions.
  
• Avoid granting administrator or root access unless necessary.
  

2. Regularly Patch and Update Systems

• Keep operating systems, software, and applications up to date.
  
• Apply security patches promptly to fix known vulnerabilities.
  
• Use automated patch management tools for efficiency.
  

3. Secure Configuration of Sudo, SUID, and Services

• Limit sudo access to trusted users and define precise rules in /etc/sudoers.
  
• Audit and remove unnecessary SUID/SGID binaries on Linux systems.
  
• On Windows, fix misconfigurations like unquoted service paths and weak service permissions.
  

 4. Conduct Regular Security Audits and Penetration Tests

• Perform vulnerability scans to identify security weaknesses.
  
• Use tools like LinPEAS, WinPEAS, PowerUp, and SharpUp to test for privilege escalation vectors.
  
• Address any misconfigurations or excessive privileges found during tests.
  

5. Harden the Operating System

• Disable unused services and features.
  
• Enforce strong permissions on system files and configuration directories.
  
• Use security frameworks like SELinux, AppArmor, or Windows Group Policy.
  

6. Monitor User and System Behavior

• Implement SIEM tools to monitor logs and detect anomalies.
  
• Track command usage and logon behavior using tools like auditd (Linux) or Event Viewer (Windows).
  
• Set alerts for suspicious activities like unauthorized privilege changes or failed admin commands.
  

7. Use Multi-Factor Authentication (MFA)

• MFA is required for all users, especially those with administrative access.
  
• Combine with strong password policies and regular password changes.
  
• Limit exposure from credential theft or reuse.
  

8. Restrict Access to Sensitive Files and Data

• Set proper file permissions to prevent unauthorized modification.
  
• Avoid storing passwords in plaintext inside scripts or config files.
  
• Use secure vaults like HashiCorp Vault, AWS Secrets Manager, or Azure Key Vault to manage secrets.
  

 9. Limit Long-Term Privileged Sessions

• Use Just-in-Time (JIT) access and temporary privilege escalation.
  
• Implement Privileged Access Management (PAM) tools to manage and monitor elevated rights.
  
• Automatically revoke privileges after tasks are completed.
  

10. Educate and Train Users and Administrators

• Train users to recognize phishing attempts and suspicious behavior.
  
• Ensure system admins understand secure configurations and privilege controls.
  
• Promote cybersecurity awareness across the organization.
  

Conclusion

Preventing privilege escalation attacks is vital to maintaining the security and integrity of any system. Organizations can significantly reduce the risk of attackers gaining unauthorized high-level privileges by applying strong access controls, keeping systems updated, monitoring for suspicious activity, and educating users. A layered, proactive defense approach is the best way to protect against these serious threats.

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