SSH Host Key Verification Bypass Allows Man-in-the-Middle Attack on Remote Sessions

Claude Desktop's SSH remote development feature verified only whether a hostname existed in ~/.ssh/known_hosts without comparing the server's presented host key against the stored key. This allowed a network-positioned attacker to present an arbitrary SSH host key and have the connection silently accepted, enabling a man-in-the-middle attack on remote development sessions. Successful exploitation required the attacker to be in a network position to intercept SSH traffic (e.g., via ARP spoofing, rogue Wi-Fi, or DNS poisoning) and the target hostname to already have an entry in the victim's known_hosts file.

Users on standard Claude Desktop auto-update have received this fix already. Users performing manual updates are advised to update to the latest version.

Thank you to hackerone.com/masato_anzai for reporting this issue.