The correct action is to mount the share, create a setuid binary owned by root, then execute it on the client. This works because the no_root_squash NFS export option tells the server to trust the client’s root user, meaning any file created by root on the client retains root ownership on the server. By placing a setuid binary—such as a copy of /bin/bash with the setuid bit set—onto the mounted share, any local user on the client can run that binary and instantly gain root privileges, since the binary executes with the file owner’s identity. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of NFS misconfigurations as a privilege escalation vector; a common trap is assuming you need to exploit the server itself, when the real vulnerability is the client’s ability to impersonate root on the exported filesystem. Remember the mnemonic: “No squash, root’s stash—setuid gives the client a bash.”
CEH Enumeration and System Hacking Practice Question
This CEH practice question tests your understanding of enumeration and system hacking. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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, you enumerate a Linux NFS server and discover that the /export directory is mounted with 'no_root_squash' and 'world_readable' permissions. Which of the following actions would allow you to escalate to root access on the NFS client?
Create a symbolic link to /etc/shadow on the server from the client
Why wrong: Symbolic links do not bypass permissions; the server enforces access control.
B
Use 'showmount -e' to list exports and then mount the share with 'mount -t nfs -o vers=3'
Why wrong: This is standard mounting, not an escalation technique.
C
Mount the share, create a setuid binary owned by root, then execute it on the client
Since no_root_squash is disabled, files created as root on the client retain root ownership on the server. A setuid binary executes with root privileges.
D
Run 'sudo nmap --script nfs-ls' to list files on the export
Why wrong: This only lists files, does not escalate privileges.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Mount the share, create a setuid binary owned by root, then execute it on the client
Option D is correct. With 'no_root_squash', a root user on the client can create files owned by root on the server. By mounting the share and creating a setuid binary owned by root, any local user on the client can execute it with root privileges.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create a symbolic link to /etc/shadow on the server from the client
Why it's wrong here
Symbolic links do not bypass permissions; the server enforces access control.
✗
Use 'showmount -e' to list exports and then mount the share with 'mount -t nfs -o vers=3'
Why it's wrong here
This is standard mounting, not an escalation technique.
✓
Mount the share, create a setuid binary owned by root, then execute it on the client
Why this is correct
Since no_root_squash is disabled, files created as root on the client retain root ownership on the server. A setuid binary executes with root privileges.
Related concept
Authentication checks who the user is.
✗
Run 'sudo nmap --script nfs-ls' to list files on the export
Why it's wrong here
This only lists files, does not escalate privileges.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CEH questions on access control and AAA configuration.
Enumeration and System Hacking — This question tests Enumeration and System Hacking — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Mount the share, create a setuid binary owned by root, then execute it on the client — Option D is correct. With 'no_root_squash', a root user on the client can create files owned by root on the server. By mounting the share and creating a setuid binary owned by root, any local user on the client can execute it with root privileges.
What should I do if I get this CEH question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CEH questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
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