It is a known issue : KB5012170 security update will lock the computer and show the bitlocker screen after a reboot. Apparently that's not the case for all configurations, but the bug has been encountered on Windows 8, 10 and 11.<p>We are a small startup with ~20 windows laptops, with recent hardware and legit licences. And since a few days it's chaos because everyone is having the bitlocker message and is not always able to find its recovery key (without the key you lose all your data). Because finding the key requires you to remember which email address you used to create your Microsoft account, and because for some reasons sometimes the key doesn't even show up on the account.<p>I'm the CTO in charge and I'm doing all the sys admin stuff myself, which is probably not a good idea as it appears now.
Up to now I had never heard about bitlocker (I don't use windows myself). I guess that's the case for many small organizations or individuals. This bug is a ticking time bomb for all of them. I'm baffled to say the least, that such a scenario can even occur. It has caused more damage to us than any ransomware attacks.<p>I'd be interested to hear if some you have experienced this situation and how you dealt with it.
Cheers
BitLocker does validation of the Platform Configuration Register (PCR) in the Trusted Platform Module (TPM). It does this to prevent a whole slew of exploitation techniques.<p>PCR banks 0 to 7 have well-defined values, so an accumulator in the TPM hashes the values and BitLocker uses the values as part of the encryption key derivation algorithm. If the PCR hash changes, the BitLocker key will become invalid.<p>However, BitLocker can have several "protectors" as they are called. One that is enabled by default is a "Recovery Key" protector, which is not protected by the TPM. It is a 48 digit password that must either be printed, stored on a non-encrypted medium (like an USB device) or uploaded to an Azure AD or Microsoft account.<p>Your colleagues must have enabled BitLocker themselves, as it is not enabled by default. They must also have been through the "backup recovery key" process, as BitLocker requires manual user interaction for this part.<p>It sucks when there is an update to PCR banks - and usually the update won't install if PCR7 binding is enabled - but users that enable advanced security features also have part of the responsibility to ensure they don't get locked out of their own systems.