If you happened to forget iCloud Keychain Security Code, you can change or reset iCloud Keychain security code from an approved device that also uses your iCloud Keychain.
If you can access an approved device that uses your iCloud Keychain, you can create a new iCloud Security Code. If no devices are available, reset iCloud Keychain.
Step 1: Go to Settings > iCloud > Keychain > Advanced.
Step 2: Tap Change Security Code.
Step 3: Enter a new iCloud Security Code.
Tips: You can also tap on Advanced Options to choose a more complex code or have one generated for you. After done, iCloud will update the information to use the new security code.
