CISSP Security Architecture and Engineering Practice Question
During a security audit, a vulnerability scanner reports a buffer overflow vulnerability in a legacy application. The application runs on a system with Data Execution Prevention (DEP/NX) enabled and Address Space Layout Randomization (ASLR) active. Which of the following is the most likely impact of these mitigations on a typical stack-based buffer overflow exploit?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
They make it harder to execute arbitrary code via injected shellcode
DEP prevents code execution in data segments like the stack. ASLR randomizes memory addresses, making it harder for an attacker to redirect execution to injected code. Combined, they significantly raise the bar.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
They only protect heap-based overflows, not stack-based
Why it's wrong here
Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) are designed to protect against memory corruption exploits across various memory regions. DEP specifically marks memory pages, including both the stack and the heap, as non-executable, preventing malicious code from running from these data segments. ASLR randomizes the base addresses of critical program components, such as the stack, heap, and shared libraries, making it difficult to predict their locations regardless of where the overflow occurs.
- ✗
They completely prevent any exploitation of buffer overflows
Why it's wrong here
While Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) are powerful mitigations, they do not completely prevent all buffer overflow exploitations. Sophisticated attackers can bypass these protections using techniques like Return-Oriented Programming (ROP), which chains existing legitimate code snippets (gadgets) in memory to achieve arbitrary execution without injecting new code. Additionally, information disclosure vulnerabilities can sometimes be leveraged to defeat ASLR's randomization.
- ✓
They make it harder to execute arbitrary code via injected shellcode
Why this is correct
This statement is correct because Data Execution Prevention (DEP) directly prevents the execution of code from non-executable memory regions, such as the stack and heap, where injected shellcode typically resides. Concurrently, Address Space Layout Randomization (ASLR) randomizes the memory addresses of key program components, making it extremely challenging for an attacker to reliably predict the exact location of their injected shellcode or necessary return addresses. Together, these mechanisms significantly increase the difficulty and complexity of exploiting buffer overflows with injected shellcode.
- ✗
They have no effect on buffer overflow exploits
Why it's wrong here
The assertion that DEP and ASLR have no effect on buffer overflow exploits is incorrect, as they are fundamental operating system-level security mitigations specifically designed to counter such vulnerabilities. Data Execution Prevention (DEP) prevents an attacker from executing malicious code placed in data segments like the stack or heap. Address Space Layout Randomization (ASLR) complicates exploitation by randomizing memory addresses, making it difficult to reliably target specific functions or injected shellcode required for a successful exploit.
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Security Governance and Principles
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
Key term
Audit
An audit is a systematic, independent review of IT systems, processes, and controls to verify compliance with policies, standards, and regulations.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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