The untethered jailbreak for iOS4.2.1 for all devices was promised along time ago (Christmas). However, no jailbreak for all devices came out, at most untethered for 4th gen devices that required SHSH blobs for it to work. FInally, the Chronic Dev Team has upgraded their greenpois0n jailbreak tool to work on iOS4.2.1 (The tool is for Mac OSX only) The tool is available HERE Note: Only the Mac OSX version of the tool has been upgraded to jailbreak iOS4.2.1; Windows users have to wait a bit longer. Instructions 1. Upgrade iDevice to iOS4.2.1 (Do NOT upgrade if you depend on an unlock!) 2. Run greenpois0n and follow on screen instructions. 3. Turn on iDevice once done, open Loader.app and install Cydia. 4. Enjoy. Little comment, I had to try this 3 times to get it to finally work. Works now though. However, I wasn't the only one with that problem.