PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).
CVSS Scores & Vulnerability Types
CVSS Score
5.8
Confidentiality Impact
Partial (There is considerable informational disclosure.)
Integrity Impact
Partial (Modification of some system files or information is possible, but the attacker does not have control over what can be modified, or the scope of what the attacker can affect is limited.)
Availability Impact
None (There is no impact to the availability of the system.)
Access Complexity
Medium (The access conditions are somewhat specialized. Some preconditions must be satistified to exploit)
Authentication
Not required (Authentication is not required to exploit the vulnerability.)