The correct answer is that an attacker can force the server to renegotiate TLS handshakes repeatedly, causing resource exhaustion. This vulnerability, tracked as CVE-2011-1473, exploits the TLS renegotiation feature when a server lacks proper rate limiting; an attacker opens multiple connections and continuously requests renegotiation, forcing the server to burn excessive CPU cycles on cryptographic handshake calculations until it becomes unresponsive. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of application-layer denial-of-service vectors that bypass traditional network flood defenses—Nessus flags it as 'High' severity because even a single attacker can cripple a server. A common trap is confusing this with the man-in-the-middle renegotiation flaw (CVE-2009-3555), but remember: the DoS variant is about *resource exhaustion*, not session hijacking. Memory tip: think "Renegotiate = Recalculate = Resource drain."
CEH Footprinting, Reconnaissance and Scanning Practice Question
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. 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 vulnerability scan using Nessus, a security analyst discovers that the target host shows a 'High' severity vulnerability for 'SSL/TLS Renegotiation DoS'. What does this vulnerability indicate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
An attacker can force the server to renegotiate TLS handshakes repeatedly, causing resource exhaustion
Option D is correct because the SSL/TLS Renegotiation DoS vulnerability (CVE-2011-1473) occurs when a server supports TLS renegotiation without proper rate limiting. An attacker can open multiple connections and repeatedly request renegotiation, causing the server to consume excessive CPU resources for cryptographic handshake calculations, effectively leading to a denial of service. Nessus flags this as 'High' severity because it can exhaust server resources even with a single attacker.
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.
✗
The server does not validate SSL certificates
Why it's wrong here
Certificate validation is not related to renegotiation DoS.
✗
The server supports SSLv2
Why it's wrong here
SSLv2 support is a different vulnerability; renegotiation DoS affects TLS as well.
✗
The server allows weak cipher suites
Why it's wrong here
Weak ciphers are a separate issue; renegotiation DoS is about the renegotiation process.
✓
An attacker can force the server to renegotiate TLS handshakes repeatedly, causing resource exhaustion
Why this is correct
This is the definition of the SSL/TLS Renegotiation DoS vulnerability.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse this DoS vulnerability with weak cipher suites or protocol version issues, but the core distinction is that renegotiation DoS is about resource exhaustion from repeated handshakes, not about encryption strength or certificate trust.
Detailed technical explanation
How to think about this question
TLS renegotiation allows a client and server to renegotiate cryptographic parameters within an existing TLS session. The attack exploits the fact that each renegotiation requires the server to perform asymmetric cryptographic operations (e.g., RSA or Diffie-Hellman key exchange), which are computationally expensive. In a real-world scenario, a single attacker using a tool like 'thc-ssl-dos' can open hundreds of connections and continuously trigger renegotiation, overwhelming a server with limited CPU capacity, even if the server uses strong ciphers and validates certificates.
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 practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: An attacker can force the server to renegotiate TLS handshakes repeatedly, causing resource exhaustion — Option D is correct because the SSL/TLS Renegotiation DoS vulnerability (CVE-2011-1473) occurs when a server supports TLS renegotiation without proper rate limiting. An attacker can open multiple connections and repeatedly request renegotiation, causing the server to consume excessive CPU resources for cryptographic handshake calculations, effectively leading to a denial of service. Nessus flags this as 'High' severity because it can exhaust server resources even with a single attacker.
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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Question Discussion
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