A Windows 11 zero-day exploit called YellowKey allows attackers to completely bypass BitLocker disk encryption without cracking the cryptography — it's a logic flaw in the implementation, not a weakness in the encryption itself. The vulnerability is confirmed by multiple security outlets and public proof-of-concept code is now available, meaning Windows users should treat BitLocker as ineffective against attackers with local device access. Microsoft has not yet released a patch, so the recommended immediate mitigation is enabling a BIOS password and BitLocker PIN to prevent attackers from accessing the boot process where the bypass works.