doorLock DoS Vulnerability in Apple HomeKit

Researchers discovered a new persistent DoS vulnerability, dubbed ‘doorLock,’ affecting the Apple HomeKit in iOS 14.7 through 15.2.

HomeKit is a software framework by Apple, available in iOS/iPadOS that lets users configure, communicate and control smart-home appliances using Apple devices. It provides users with a way to automatically discover such devices and configure them.

An attacker could trigger the vulnerability by changing the name of a HomeKit device to a string larger than 500,000 characters. Upon loading the string, iOS and iPadOS devices will reboot and will be unusable. The vulnerability can only be exploited by attackers with access to the victim’s ‘Home’ or via manually accepting an invitation to one.

In order to solve the issue, it is necessary to force a reset of the device that will cause all stored data to be removed. The only way to recover the removed data will be to restore a working backup.

Once the device reboots and the user signs into the same iCloud account linked to the HomeKit device, the doorLock bug will be triggered again.

he issue could be exploited by ransomware operators to make devices unusable. It’s possible to avoid the exploitation of this issue by disabling Home devices in Control Center. Users are also recommended to be vigilant to invitations to join Home networks of other users.

In order to regain normal access to the iCloud account linked to the data, it is possible to perform the following steps.

If you are not able to install the testing application:

1. Restore the affected device from Recovery or DFU Mode
2. Setup the device as normal, but do NOT sign back into the iCloud account
3. After setup is finished, sign into iCloud from settings. Immediately after doing so, disable the switch labeled “Home.” The device and iCloud should now function again without access to Home data.

If you are able to install the testing application with Xcode and wish to regain access to Home Data:

1. Restore the affected device from Recovery or DFU Mode
2. Setup the device as normal, but do NOT sign back into the iCloud account
3. After setup is finished, sign into iCloud from settings.
4. Press the back button and then press Control Center settings again to reload the page, and repeat this until a setting labeled “Show Home Controls” is visible. Immediately disable the setting.
5. Install the test application and run it with a short string to rename all associated Home devices.