New downgrade attack can bypass FIDO auth in Microsoft Entra ID

Security researchers have created a new FIDO downgrade attack against Microsoft Entra ID that tricks users into authenticating with weaker login methods, making them susceptible to phishing and session hijacking.

These weaker login channels are vulnerable to adversary-in-the-middle phishing attacks that employ tools like Evilginx, enabling attackers to snatch valid session cookies and hijack the accounts.

Although the attack doesn't prove a vulnerability in FIDO itself, it shows that the system can be bypassed, which is a crucial weakness.

This is especially worrying considering the increased adoption of FIDO-based authentication in critical environments, a consequence of the technology being touted as extremely phishing-resistant.

FIDO passkeys are a passwordless authentication method