Google Passkey Flaw: Hackers Could Hijack Your Passkeys via Malware

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Palo Alto Networks’ Unit 42 detailed three Google passkey exploits

Attacks require prior malware infection; methods ranged from impersonating victims to stealing the master secret protecting synced passkeys

Google implemented fixes after disclosure, with some services (e.g., eBay) patching vulnerabilities directly

Security researchers from Palo Alto Networks’ Unit 42 have found three ways to exploit Google’s passkey system and log into people’s PIN- or biometrics-protected accounts.

They named these ways ‘Pass-ta-key’, ‘Silver Pass-ta-key’, and ‘Golden Pass-ta-key’, each being progressively more dangerous than the previous one.

While it sounds mighty dangerous, there are major caveats to the exploit, and some of the holes have been plugged already.

Trusting the wrong device

The biggest caveat is that the victim’s device needs to be infected with malware beforehand. Malware can do all sorts of things, from stealing session cookies to exfiltrating sensitive data, so if a device is tainted with malware, it’s already in trouble.

Still, Unit 42’s findings were important enough to warrant a fix from Google.

In the first technique, the attackers pretend to be the victim. By using malware, they can “ask” Google to log into a passkey-protected account as if it was the victim themselves. Usually, the service being logged into would require a PIN or a fingerprint to confirm the authenticity of the request, but in this scenario, that wasn’t the case.

The method doesn’t work everywhere, though. Unit 42 could not replicate the attack on GitHub, but they succeeded on eBay. The latter later fixed the problem.

In the second attack, Unit 42 managed to make Google “trust” the threat actor’s device, meaning the victim’s computer was no longer necessary.

In the third attack, the researchers managed to steal the “master key”.

Google Password Manager syncs the passkeys between devices, and to do that, it uses a master secret that protects all of the synced passkeys. The researchers found that, under certain circumstances, malware can grab this master secret while Chrome is temporarily using it, unlocking all of the synced passkeys, copying them to another computer, and being able to use them at a later date.

The researchers disclosed their findings with Google before publication, and some fixes were already implemented. Google is yet to comment on the findings and confirm that all of the flaws were addressed.

Via BleepingComputer