How to Jailbreak iOS 4.2.1 with Greenpoison RC5 on iPhone, iPad and iPod Touch [Guide]

Chronic Dev Team has just released Greenpois0n RC5 to apply untethered jailbreak on iOS 4.2.1 devices. Greenspoison rc5 supports these idevices – iPhone 4, iPhone 3GS,, iPad, iPod Touch 3G and iPod Touch 4G.

Unlike Redsn0w 0.9.7, Greenpoison RC5 doesn’t require you to have SHSH Blobs of iOS 4.2b3 or iOS 4.1 on Cydia servers. Find complete step by step tutorial after the break.

Since Windows version of Greenpois0n RC5 is not released yet, so this guide is for Mac users only.

Disclaimer: This guide is posted for testing and educational purposes only. Follow it at your own risk. We won’t be responsible for any damage to your any device.

Part 1: How to Jailbreak (Untethered) iOS 4.2.1 with Greenpoison rc5 if You Don’t Rely on Unlock

Step 1:Back up your device first using iTunes.

Step 2: Restore to fresh iOS 4.2.1 firmware version. (If you rely on unlock, please read the Part 2. Never restore to Fresh iOS 4.2.1 because it will update the baseband and you may loose the ability to unlock)

Step 3: Download Greenpoison RC5, extract it and run it.

Step 4: Click on “Jailbreak” button and follow the instructions to put your device into DFU mode.

  • Press and hold the sleep button for 2 seconds
  • Continue holding sleep; press and hold home for 10 seconds.
  • Release sleep button; continue holding home for 15 seconds.

Step 5: Once your device is into DFU mode, the jailbreak process starts.

Important! At this point your device may stuck at “Greenpoison Initialized” error on your device. Simply run Greenpoison and put your device into DFU mode again and jailbreak. Some users may experience “Laptop Freeze” condition, even I faced this problem, and in this case restart your Mac machine and try again.

Step 6: After the successful jailbreak your iPhone will restart.

Step 7: You will notice a new Loader icon on springboard. Press to launch it, install Cydia. Once Cydia is installed on your iPhone 4, iPhone 3GS etc, you will prompted whether you want to remove the Loader or not. Press the remove button and then press Home button.

Step 7: You have successfully jailbroken (untethered) your device on latest iOS 4.2.1.

Part 2: Untethered Jailbreak with Greenpois0n if You Rely on Unlock

I don’t know Greenpois0n support hacktivation or not, at least it didn’t work on my iPhone 3GS which was updated to iPad baseband 06.15.00, so I used this method to get untethered jailbreak state and hacktivation.

It is to remind you that if you rely on unlock, don’t use the fresh stock iOS 4.2.1 firmware. Instead of that, restore to custom hacktivated iOS 4.2.1 while preserving the baseband. You can also use Redsn0w to hacktivate your iDevice as mentioned below. You can use PwnageTool to cook a custom iOS 4.2.1 version.

Note: I tested this method on iPhone 3GS only.

a) Make it sure you have custom hacktivated iOS 4.2.1 firmware prepared with Pwnagetool.

b) Put your device into Limera1ned DFU mode using Redsn0w 0.9.6 b5 or above.

c) Connect your device with PC and restore to custom hacktivated iOS 4.2.1 firmware using iTunes.

d) Now follow the above mentioned procedure from Step 3 to Step 6.

Step 7: If you are using custom iOS, and on unsupported carrier and Greenpois0n doesn’t hacktivate your device,  you will see “Emergency Mode” screen when your mobile starts after the successful Greenpoison jailbreak.

Step 8: Restart your device for one more time and your will notice an animated Greenpoison bootlogo if you have successfully jailbroken your device.

Step 9: Now open Redsn0w 0.9.6 b5 or above, click on “Install Cydia” option only and follow the  on-screen instruction. Redsn0w will not only install the missing Cydia but also hacktivate your device.

Step 10: Once the jailbreak process, using Redsn0w this time, completes, your iPhone will reboot and you won’t see “Emergency Call” screen any more.

Step 11: Install Ultrasn0w from Cydia using Wifi. Restart your phone.

Your device is now jailbroken (untethered) and unlocked on iOS 4.2.1. Cheers.

Requirements and Downloads:

  • Download Greenpois0n RC 5 (Win version is here)
  • Download iOS 4.2.1 for your device if you don’t rely on unlock
  • Custom basebad preserved iOS 4.2.1 if you rely on unlock
  • iTunes 10.0 +
  • Download Redsn0w 0.9.6b5 or above version
  • Pwnagetool to cook custom firmware
  • Mac machine

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Updated 12 years agoCategorized as Tutorials

By A. Usman

Loves new tech, especially from Apple and Google.

View all of A. Usman's posts.

17 Replies

  1. Hellosays:

    Can i jailbreak iphone 3g 4.2.1 also with greenposion?

  2. Joaorf7says:

    I Jailbreak my Iphone 3GS 4.2.1 with greenpoison, this program run perfect, it instaled Cydia, then with redsnow, it appeard Winter board, but I only have a problem, I change SIM card from one operator to other and it doesn’t work, can you tell me if I have to run some other app?

    1. It is called unlocking and it depends on the modem firmware (baseband) of your device. Were you using official carrier SIM card when you jailbreaked it or is your device factory unlocked? If it is locked to any network , tell me the current baseband (modem firmware) of your device [ Settings -> General -> About -> Modem Firmware] and I will suggest you the possible solutions. And if is factory unlocked, you should be able to use any SIM card.

  3. Caiocpsays:

    I did everything u said in this post but the Loader app is not working, i click on it and nothing happens…… what should i do?

  4. Danielroblesnoriegasays:


  5. chiesays:

    i was able to jailbreak my iphone4 but its still lock how do i unlock it???? plz….. help….

  6. thisarasays:

    Thank you very much…….. :)
    This works fine with my iphone4 4.0.2 with baseband 1.59.00. And now its working on 4.2.1 & baseband 1.59.00 with jailbeark and unlock. Perfect…..
    I was waiting for this for soooo long….

  7. Kevin Msays:

    How Can i Unlock my Iphone 3gs with 4.2.1 which is already jailbroken using Greenpois0ns latest version? My baseband is 5.15. A) Do I need to upgrade my baseband? B) What do I do after..?


  8. Sen Pereirasays:

    I have iPhone 3GS with baseband 5.15. I upgraded the iOS by mistake to 4.2, without saving anything. Now what I have understood is that if want to unlock it, i will need to upgrade the baseband to 6.15. Is it true? Is there anyway to unlock it without changing the baseband? Please help. Thanks.

    1. No other way except upgrading it to baseband 6.15.

  9. Raindropsays:

    i want to know, what is difference between Greenposion and Redsnow?
    my iPod iOS 4.2.1 already jailbreak with Redsnow. Just now Greenposion is release, but it also need Redsnow. So, i want to know difference between Greenposion and Redsnow.

  10. anup756says:

    I have an iPhone 3GS 16 GB with Ipad baseband ie. 06.15.00. Can I jailbreak untethered without restoring it to custom firmware? Directly starting from Step: 3.

  11. With your Pwnagetoold 4.2.1 firmware for 3GS, is that still using the iPad firmware/baseband? Is there a way to back out of that yet?

    1. Yes, iPad baseband. And you can’t go back but a tool is being developed to downgrade the baseband.

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