The latest version of Redsn0w, that is Redsnow 0.9.6 RC15, does not support the untethered jailbreak on the recently released iOS 4.2.8. The one way to get the untethered jailbreak on your CDMA iPhone 4 is to cook the custom iOS 4.2.8 with Sn0wbreeze 2.7 and then restore to it. But if you are a Mac user, you can’t use Sn0wbreeze because the said software is compatible with Win OS only.
Here is a simple guide by following which you can get untethered jailbreak on you Verizon iPhone 4 without needing Snowbreeze or restoring to custom iOS 4.2.8.
Step 1: Update your Verizon iPhone 4 to iOS 4.2.8 via iTunes.
Step 3: While selecting “Install Cydia” option, jailbreak your phone.
Step 4: Now boot tethered your iPhone using the “Just boot tethered right now” option from Redsnow.
Step 5: Launch Cydia and add the source http://djayb6.com.
Step 6: Using the search box in Cydia, search for “CDMA iPhone Untether”
Step 7: Install CDMA iPhone untether for iOS 4.2.8 package.
Step 8: Restart your untethered jailbroken iPhone 4 running on Verizon network.
Thanks to Djayb6 for developing this package and making iOS 4.2.8 unethered jailbreak possible.