Terrapin Attack Breaking Down SSH Security

Navigating the Terrapin Attack Landscape — Understanding, Detecting, and Mitigating SSH Vulnerabilities

Introduction

SSH (Secure Shell) serves as a crucial internet standard, providing secure access to network services, including remote terminal login and file transfer across organizational networks and over 15 million servers on the open internet.

Terrapin Attack Overview

The Terrapin attack, a prefix truncation assault on the SSH protocol, disrupts the integrity of the secure channel by manipulating sequence numbers during the handshake. This manipulation allows an attacker to remove messages at the channel’s initiation, downgrading connection security by truncating extension negotiation messages. Such truncation can compromise client authentication algorithms and deactivate specific countermeasures in OpenSSH 9.5.

Implementation Flaws and Exploitation

Terrapin extends its impact by exploiting implementation flaws. Weaknesses in the AsyncSSH servers’ state machine enable attackers to sign a victim’s client into another account…