The answer is an XML External Entity (XXE) injection attack. This is correct because the vulnerability arises when an XML parser processes external entities defined in a Document Type Definition (DTD); by crafting a malicious payload that references a local file, such as `file:///etc/passwd`, the attacker forces the server to read and return the contents of that file in the response. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of XML-based data transmission risks and is often presented as a web application or API security question. A common trap is confusing XXE with Server-Side Request Forgery (SSRF), but remember that XXE specifically exploits XML entity parsing to read files, while SSRF targets internal network resources. For a quick memory tip, think “XXE = eXternal Entity eXfiltration” to recall that the core action is reading files from the filesystem via external entities.
CEH Web Application and Injection Attacks Practice Question
This CEH practice question tests your understanding of web application and injection attacks. 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.
A security engineer observes that an internal web application uses XML to transmit data between systems. The engineer discovers that by sending a crafted XML payload, they can read sensitive files from the server's filesystem. Which attack is being performed?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
XXE injection
XXE (XML External Entity) injection allows reading files via external entities in XML.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
SSRF
Why it's wrong here
SSRF involves making the server request internal resources, but reading files directly via XML is XXE.
✗
Command injection
Why it's wrong here
Command injection executes system commands, but the description indicates reading files through XML, not shell commands.
✓
XXE injection
Why this is correct
XXE injection exploits XML parsers that process external entities, allowing file disclosure.
Related concept
Static NAT maps one inside address to one outside address.
✗
XPath injection
Why it's wrong here
XPath injection targets XPath queries, not reading files via XML entities.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
Command injection executes system commands, but the description indicates reading files through XML, not shell commands.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CEH NAT questions on configuration and troubleshooting.
Web Application and Injection Attacks — This question tests Web Application and Injection Attacks — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: XXE injection — XXE (XML External Entity) injection allows reading files via external entities in XML.
What should I do if I get this CEH question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CEH NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A web application is vulnerable to XML External Entity (XXE) injection. Which THREE of the following are potential impacts of successfully exploiting an XXE vulnerability?
easy
A.SQL injection
✓ B.Arbitrary file read on the server
✓ C.Denial of Service (DoS)
✓ D.Server-Side Request Forgery (SSRF)
E.Remote code execution via command injection
Why B: XXE can be used for reading local files (e.g., /etc/passwd), performing SSRF by making the server issue requests, and causing denial of service (e.g., billion laughs attack).
Last reviewed: Jun 21, 2026
Question Discussion
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