The correct technique is to run /usr/bin/less with sudo and then type !/bin/bash to spawn a root shell. This works because the less utility, when invoked with elevated privileges, includes a built-in shell escape feature that allows executing arbitrary commands from its interactive prompt; by typing an exclamation mark followed by a command, the user effectively runs that command with the same privileges as the less process. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of Linux privilege escalation through misconfigured sudo entries, often appearing in the system hacking or post-exploitation domains. A common trap is forgetting that less is not just a pager—it can execute system commands, so simply reading a file with sudo does not escalate unless you use the escape. Memory tip: think of the exclamation mark as a “bang” that blasts you into a root shell.
CEH Vulnerability Analysis and System Hacking Practice Question
This CEH practice question tests your understanding of vulnerability analysis and system hacking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During a penetration test, a tester gains access to a Linux system and needs to escalate privileges. The tester finds that the user has sudo privileges to run /usr/bin/less as root without a password. Which technique should the tester use to escalate privileges?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run /usr/bin/less with sudo, then type !/bin/bash to spawn a root shell
Option B is correct because when a user has sudo privileges to run /usr/bin/less as root without a password, the tester can leverage the fact that less can execute shell commands from within its interface. By running 'sudo /usr/bin/less' and then typing '!/bin/bash', the tester spawns a root shell, effectively escalating privileges to root.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Exploit a kernel vulnerability using a local exploit
Why it's wrong here
Kernel exploits are risky and may not be necessary.
✓
Run /usr/bin/less with sudo, then type !/bin/bash to spawn a root shell
Why this is correct
less allows command execution via ! when run with elevated privileges.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use the find command with -exec to execute a shell
Why it's wrong here
find -exec requires find to be SUID or sudo, which is not the case.
✗
Check for world-writable scripts in cron jobs
Why it's wrong here
This could work but is not the immediate method given the sudo privilege.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may overlook the command execution capability of less and instead focus on kernel exploits or cron jobs, missing the direct and simplest path to root via the sudo misconfiguration.
Detailed technical explanation
How to think about this question
The less command, when invoked with sudo, runs as root and retains its ability to execute shell commands via the '!' escape sequence. This is a classic example of abusing sudo rights on a pager program (less, more, or most) that allows command execution. In real-world scenarios, such misconfigurations often appear in sudoers entries like 'user ALL=(root) NOPASSWD: /usr/bin/less', which should be restricted by using the 'NOEXEC' tag or by avoiding pager programs in sudo.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Vulnerability Analysis and System Hacking — This question tests Vulnerability Analysis and System Hacking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run /usr/bin/less with sudo, then type !/bin/bash to spawn a root shell — Option B is correct because when a user has sudo privileges to run /usr/bin/less as root without a password, the tester can leverage the fact that less can execute shell commands from within its interface. By running 'sudo /usr/bin/less' and then typing '!/bin/bash', the tester spawns a root shell, effectively escalating privileges to root.
What should I do if I get this CEH question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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