GPEN · Question #16
Which of the following statements are true about MS-CHAPv2? Each correct answer represents a complete solution. Choose all that apply.
The correct answer is B. It can be replaced with EAP-TLS as the authentication mechanism for PPTP. C. It provides an authenticator-controlled password change mechanism. D. It is subject to offline dictionary attacks.. MS-CHAPv2 is a connection-oriented mutual authentication protocol used with PPTP that supports password change mechanisms but contains well-known cryptographic weaknesses enabling offline attacks.
Question
Which of the following statements are true about MS-CHAPv2? Each correct answer represents a complete solution. Choose all that apply.
Options
- AIt is a connectionless protocol.
- BIt can be replaced with EAP-TLS as the authentication mechanism for PPTP.
- CIt provides an authenticator-controlled password change mechanism.
- DIt is subject to offline dictionary attacks.
How the community answered
(62 responses)- A19% (12)
- B81% (50)
Why each option
MS-CHAPv2 is a connection-oriented mutual authentication protocol used with PPTP that supports password change mechanisms but contains well-known cryptographic weaknesses enabling offline attacks.
MS-CHAPv2 is connection-oriented, operating within PPTP which establishes a persistent tunnel - it is not a connectionless protocol like those built on UDP.
EAP-TLS can be configured as a replacement for MS-CHAPv2 as the inner authentication method within PPTP tunnels, substituting certificate-based mutual authentication for the weaker password-based exchange.
MS-CHAPv2 includes an authenticator-controlled password change mechanism defined in RFC 2759, allowing the authenticating server to mandate a password update during the authentication handshake.
MS-CHAPv2 challenge and response values captured from network traffic can be subjected to offline dictionary or brute-force attacks, a well-documented weakness that tools such as asleap actively exploit.
Concept tested: MS-CHAPv2 authentication properties and known vulnerabilities
Source: https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-chap/4740bf05-6b67-40ee-872b-e0a30f526f9e
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