The Windows 11 "patch Tuesday" update for July 2024 breaks Bitlocker drive encryption, Microsoft notes in its issue discovery. The company releases monthly major update packages for Windows, timing them on every second Tuesday of the month. The July 2024 update carries the knowledge-base identifier KB5040442, and applies to Windows 11 22H2 and 23H2. Bitlocker is a first-party disk encryption feature by Microsoft that's included with Windows 10 Pro, Windows 11 Pro, and Windows 11 Enterprise editions. You are prompted a disk decryption password at every system startup, the disk remains encrypted until either password is input, or a Bitlocker Recovery process is followed.

The KB5040442 causes Bitlocker to forget its own password, forcing you to clear the Bitlocker Recovery process. When you encrypt a volume with Bitlocker, you are given a recovery key that you're supposed to safekeep. Those with online Microsoft accounts have the option to get Microsoft to store their recovery keys, so they could log into their Microsoft account on another device (like a phone), and access the stored recovery key, which they then manually input on the borked machine to create a new Bitlocker password. Microsoft acknowledges that Bitlocker recovery is only a workaround, KB5040442 will cause machines to forget their Bitlocker passwords, and force a recovery. The company is working on an update that fixes this, so if you have an always-on machine with Bitlocker that just got patched to KB5040442, you might want to keep the recovery key handy.