The answer is return-oriented programming (ROP) using fixed address gadgets. This technique is correct because when both ASLR and NX are enabled, the stack is non-executable and memory addresses are randomized, preventing traditional shellcode injection. However, if a tester discovers a ROP gadget at a fixed address in a library not affected by ASLR—such as a binary compiled without PIE or a statically linked library—they can chain these gadgets together to redirect execution flow and achieve arbitrary code execution without ever executing code on the stack. On the CompTIA PenTest+ PT0-002 exam, this scenario tests your understanding of bypassing modern exploit mitigations; a common trap is assuming ASLR makes all addresses unpredictable, but fixed-address gadgets in non-randomized libraries remain exploitable. Memory tip: think “fixed gadgets for fixed bypass”—if the library address is static, ROP chains can still work even when the stack is non-executable and randomized.
PT0-002 Attacks and Exploits Practice Question
This PT0-002 practice question tests your understanding of attacks and exploits. 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 identifies a buffer overflow vulnerability in a Linux binary that has both ASLR and NX (Non-Executable) enabled. The tester discovers a ROP gadget at a fixed address in a library that is not affected by ASLR. Which technique can be used to exploit this vulnerability and achieve code execution?
Heap spraying to predict memory layout and inject shellcode
Why wrong: Heap spraying is often used to bypass ASLR but does not bypass NX; injected shellcode would still be non-executable.
B
Return-oriented programming (ROP) using the fixed gadgets
ROP uses fixed gadgets to create a chain that bypasses NX and, with fixed addresses, can also bypass ASLR.
C
Stack canary bypass using information leak
Why wrong: Stack canaries detect buffer overflows; bypassing them does not address NX or ASLR.
D
Format string attack to overwrite GOT entries
Why wrong: Format string attacks can overwrite memory but do not directly bypass NX; they may be used in combination, but ROP is the direct solution here.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Return-oriented programming (ROP) using the fixed gadgets
Return-oriented programming (ROP) is the correct technique because ASLR and NX are both enabled, preventing direct shellcode execution and making memory addresses unpredictable. However, the tester found a ROP gadget at a fixed address in a library not affected by ASLR, allowing the construction of a chain of gadgets to achieve arbitrary code execution without needing to inject or execute shellcode on the stack.
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.
✗
Heap spraying to predict memory layout and inject shellcode
Why it's wrong here
Heap spraying is often used to bypass ASLR but does not bypass NX; injected shellcode would still be non-executable.
✓
Return-oriented programming (ROP) using the fixed gadgets
Why this is correct
ROP uses fixed gadgets to create a chain that bypasses NX and, with fixed addresses, can also bypass ASLR.
Related concept
Read the scenario before looking for a memorised answer.
✗
Stack canary bypass using information leak
Why it's wrong here
Stack canaries detect buffer overflows; bypassing them does not address NX or ASLR.
✗
Format string attack to overwrite GOT entries
Why it's wrong here
Format string attacks can overwrite memory but do not directly bypass NX; they may be used in combination, but ROP is the direct solution here.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose heap spraying (Option A) thinking it bypasses ASLR, but they forget that NX still blocks shellcode execution, making ROP the only viable technique when fixed gadgets are available.
Detailed technical explanation
How to think about this question
ROP works by chaining small instruction sequences (gadgets) that end with a return instruction, allowing the attacker to control the stack pointer and execute arbitrary logic without injecting code. In this scenario, the fixed-address gadget is likely from a non-ASLR library (e.g., a legacy or statically linked component), which provides a stable base for the ROP chain even when the binary's own addresses are randomized. Real-world exploits often use ROP to call mprotect() to mark a memory region as executable, then jump to shellcode, effectively bypassing both NX and ASLR.
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 security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PT0-002 question in full detail.
Attacks and Exploits — This question tests Attacks and Exploits — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Return-oriented programming (ROP) using the fixed gadgets — Return-oriented programming (ROP) is the correct technique because ASLR and NX are both enabled, preventing direct shellcode execution and making memory addresses unpredictable. However, the tester found a ROP gadget at a fixed address in a library not affected by ASLR, allowing the construction of a chain of gadgets to achieve arbitrary code execution without needing to inject or execute shellcode on the stack.
What should I do if I get this PT0-002 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.
About these practice questions
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Variation 1. During a penetration test, a tester identifies a buffer overflow vulnerability in a Linux binary. The system has ASLR and NX (Non-Executable) enabled. The tester finds a ROP gadget at a fixed address in a library that is loaded at a constant address across reboots. Which exploitation method is the most appropriate to achieve code execution?
hard
A.Return-to-libc attack
✓ B.Return-Oriented Programming (ROP) chain
C.Heap spraying
D.SEH overwrite exploit
Why B: Option B is correct because Return-Oriented Programming (ROP) is specifically designed to bypass both ASLR and NX when a fixed-address ROP gadget is available. Since the library is loaded at a constant address across reboots, the tester can chain gadgets from that library to execute arbitrary code without needing to inject executable shellcode.
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Question Discussion
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