Google Password Manager Vulnerability: Passkeys Can Be Hijacked
Malware on Windows can access accounts without fingerprint or PIN verification.
1Passkey Security at Risk
Researchers revealed that malware running as a standard user on Windows can access passkey-protected accounts without fingerprint, PIN, or any additional verification. Three attack methods targeting Chrome's Google Password Manager cloud authenticator were identified. These methods target the master key protecting users' synced passkeys.
2Attack Methods
Dubbed Pass-ta-key, Silver Pass-ta-key, and Golden Pass-ta-key by Unit 42, these attacks target not cryptography but the code surrounding passkeys. Attackers can obtain valid authentication assertions, control user-verification keys, or extract the 32-byte Security Domain Secret (SDS) used to decrypt synced passkey private keys. The latter two methods provide reusable access after initial endpoint compromise.
3Chrome's Vulnerabilities
The attacks exploit weaknesses in how Chrome stores device keys, behaves during device re-enrollment, and whether sites verify human authentication. Chrome creates TPM keys without names and reloads them later without prompts. Current Chromium source code includes a TODO suggesting these keys should be labeled.
4User Verification Flag Issue
Google Cloud Authenticator returns valid assertions, distinguishable from post-user-verification ones only by the unset User Verified (UV) flag. Current Web Authentication specs require failing ceremonies when this flag is absent for userVerification-required parties. Researchers noted GitHub enforces this while eBay fixed validation gaps post-disclosure.
5Silver Pass-ta-key Method
This method involves malware forcing Chrome to re-enroll devices and registering attacker-controlled keys before user-verification keys are created. The service doesn't verify if new keys originate from secure hardware. Assertions signed with these keys carry UV flags, enabling later logins without the victim's device. Chromium source confirms new devices can retain deferred_uv_key_creation states.
6Golden Pass-ta-key Method
The most potent attack targets SDS directly. Malware triggers re-enrollment, reads the secret from Chrome's process memory while briefly in plaintext, and uses it to recover synced passkey private keys. Chromium source confirms 32-byte security-domain secrets exist in client-process data structures.
7Google's Mitigations
Researchers stated Google removed prior SDS exposure from Chrome's FIDO logs and eBay now validates UV flags. However, secrets still reach clients and remain in Chrome's memory. Google's public support docs allow Password Manager PIN changes or data deletion but lack SDS-specific rotation controls.
8Risks for Users and Companies
Uncertainty remains whether all three attack paths are fully patched. Users lack methods to check SDS exposure. Relying parties must set userVerification to required. These vulnerabilities raise questions about passkey reliability and necessitate additional user precautions.