Google Password Manager Attacks Could Let Malware Hijack Passkey-Protected Accounts

Google Password Manager Attacks 🚨

Malware running as an ordinary user on a Windows machine can sign into a victim’s passkey-protected accounts without a fingerprint, a PIN, or anything appearing on the victim’s screen. Unit 42 detailed three attack paths against Chrome’s Google Password Manager cloud authenticator, which it calls Pass-ta-key, Silver Pass-ta-key, and Golden Pass-ta-key. The strongest targets the master key protecting the user’s synced passkeys.

None of this breaks the cryptography. The attacks target the code around the passkey: how Chrome stores its device keys, how it re-enrolls a device after that state disappears, and whether the site you are signing into checks that a human was verified at all. The attacks can silently obtain a valid authentication assertion, install an attacker-controlled user-verification key, or extract the 32-byte Security Domain Secret (SDS) used to decrypt synced passkey private keys.

Attack Techniques 🔍

1. Pass-ta-key: Extracts Chrome’s wrapped device identity key and asks the TPM to sign an attacker-controlled request through Windows Cryptography API: Next Generation (CNG) calls. Google Cloud Authenticator returns a valid assertion, with only a single bit, the User Verified (UV) flag, left unset.
2. Silver Pass-ta-key: Targets the next layer. Malware forces Chrome to re-enroll the device, allowing an attacker to register their own key instead.
3. Golden Pass-ta-key: Goes after the SDS itself. Malware can trigger re-enrollment, read the secret from Chrome’s process memory while it briefly sits there in plaintext, and use it to recover synchronized passkey private keys.

Recommendations ✅

Relying parties should set userVerification to required and verify the returned UV bit rather than trusting the request setting alone. Credential providers should attest newly enrolled keys, strengthen re-registration and recovery checks, restrict access to local passkey state, and keep master keys out of client logs and memory.

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