CVE-2021-36367: Putty

High severity, CVSS 8.1. EPSS: 1.1% chance of exploitation in the next 30 days.

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).

Affected products

• Putty Putty: up to and including 0.75

Published 2021-07-09. Last modified 2026-06-17.