Untethered Jailbreak Guide for iPhone 4 and 3GS on iOS 4.2.1

February 6, 2011 — by Simon Ng24



Untethered Jailbreak Guide for iPhone 4 and 3GS on iOS 4.2.1

February 6, 2011 — by Simon Ng24

You may already know Greenpois0n has been released. The debut of Greenpois0n is prominent as it is the first stable jailbreak tool that supports untethered jailbreak on all devices running iOS 4.2.1. Unlike the Redsn0w 0.9.7, the tool doesn’t require you to have the SHSH blobs. You can simply jailbreak your device running iOS 4.2.1 out of the box.

Presently, the Greenpois0n is available on Mac platform only. If everything goes well, the Windows version will be released very soon (hopefully in these few days). Update: The Windows version is now available. I have tried to jailbreak my iPhone 4 using Greenpois0n. Despite there are a few hiccups, overall speaking, the jailbreak process is quite smooth.

Here I come up a step-by-step jailbreak guide to walk you through the process using Greenpois0n. If you’re using iPhone 3GS or iPhone 4 and would like to jailbreak your device on iOS 4.2.1, you can simply follow the procedures and achieve the jailbreaking.

Before we dive into the jailbreak process, please read through the notes very carefully:

  • As of now, the Greenpois0n is available for Mac user only. For Windows user, you have to wait for a few days before the official release. Update: The Windows version is now available.
  • Greenpois0n is a jailbreak solution that allows you to open up your device to install 3rd-party applications. It’s not a software-unlock solution. So if you are currently relying on Ultrasn0w to unlock your iPhone, please DO NOT upgrade your iPhone to iOS 4.2.1 directly. Otherwise you’ll lose the unlock and your iPhone will not be able to make call.
  • Greenpois0n does not come with hacktivation. That means you have to activate your iPhone before using the jailbreak tool.
  • Greenpois0n works only on iOS 4.1 and 4.2.1. However this guide is written based on the jailbreaking of iOS 4.2.1.
  • Make sure you’re using iTunes 10.1 or up.
  • If you have used Redsn0w to jailbreak (untethered) your iPhone, I suggest you to restore it to iOS 4.2.1 via iTunes before using Greenpois0n.

Note: If you have any questions after reading the note, feel free to leave us comment before kicking off your jailbreak journey.

Okay, let’s get started.

Preparation for the Jailbreak

1. Download Greenpois0n RC5_2 from greenpois0n.com or mirror site.

Note: I suggest you to download the tool from the mirror site. The official site is extremely busy and not very stable.

2. Extract the greenpois0n-osx_rc5_2.zip and you’ll have the “Greenpois0n” application.

Kick-off the Jailbreak Process

3. Connect your iPhone to computer via USB cable and power it off.

4. Launch the Greenpois0n application.

5. Click the “Jailbreak” button to kick off the jailbreak process. You can simply follow the on-screen instructions to put your iPhone into DFU mode. Keep holding the home button till the end of the jailbreak process.

Note: If you fail for the first time, just quit Greenpois0n, power off your iPhone and goes through the process again. It won’t hurt.

6. As you successfully put the device into DFU mode, Greenpois0n will automatically jailbreak your device. On your iPhone, you’ll see a series of status messages in command mode. That’s normal. Just wait until Greenpois0n tells you the process completes.

Installing Cydia

7. After jailbreaking, your iPhone will be automatically booted up. You should find a new icon called “Loader”. Simply tap on the icon and launch the app.

greenpois0n loader app

8. Once launched, tap on the “Cydia” button to install cydia. This will initiate the download process. Just wait for it to complete and you’ll have cydia installed on your iPhone.

greenpois0n loader app cydiagreenpois0n loader app cydia download

Note: If you found the cydia button missing after launching Loader app, just quit it and try again.

9. After successfully installing cydia, you can tap the “Option” button and remove the Loader app.

Simon Ng

Founder, developer and chief blogger of simonblog.com

  • Andy

    Does it work on Apple Tv 2g

    • Presently, it doesn’t support Apple TV. But the developer is working on a new version to support the jailbreak.

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  • Eugen

    Any idea when an unlock solution would be available?

    • No news about that yet. Will keep you posted.

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  • nick

    hi i have tried downloading this from many sites (the greenpoison rc5-2) and everytime i open it it says error the application quit unexpectedly and i have tried numerous times and it wont work. i have an iphone 4 4.2.1. i have downloaded the one from greenpois0ns website and it wont open. Is there a limera1n or anything i could use to jailbreak or will i have to wit?

  • Lycos

    I have one question : if I have a problem, can I restore the iphone and use the guarranty without any problem ?

    • Eugen

      Yep, you can always get the original firmware from apple and do a full restore to its original settings. That’s what I do on my iPhone 4 from time to time πŸ™‚

      • lavender

        Do we have to pay to get the original firmware fr Apple to do a full restore to its original settings??? Can i do a reset??

        • No,
          it’s free and you can do a full restore at anytime…

  • Dimocon

    Just a heads up, If you’ve already jailbroken iPad or iPhone 4 with redsn0w, then all you have to do is run greenpois0n and it will automatically overlap it and work perfectly with the previously already installed Cydia πŸ™‚ enjoy

  • thank you..
    its working on my iphone 4 4.2.1…

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  • Casey

    I’m having trouble getting my phone to get service! What do I need to do?

  • Greesha

    I’ve tried to jailbreak an iPhone 4 and an iPod Touch 4th generation and both of them seem to fail for some reason. I’ve jailbroken iDevices before but idk why its doing this. Is a recovery required before jailbreak?

    • Greesha

      forgot to add that they’re both 4.2.1 firmware

  • nazyr

    I have IP4 iOS 4.1(8B117) and Baseband 02.10.04,
    Jailbreak using limerain and carrier unlock from the box.

    Is is safe to update to iOS4.2?

  • omar ali

    i have an ipod touch 4g, on ios 4.2.1 and i successfully jailbreaked it using greenpoison, but I have downloaded apps but cannot install them onto my ipod, can anyone tell me what the problem is?

  • omar ali

    i have an ipod touch 4g, on ios 4.2.1 and i successfully jailbreaked it using greenpoison, but I have downloaded apps but cannot install them onto my ipod, can anyone tell me what the problem is?please can you reply asap…thank you!

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  • M0N15H

    Please excuse me, as these JB, Untethered, etc.. terms are not easy for me. But, I am still expecting help from you personally, as you could understand this best.
    My Phone : iphone 3GS
    Version : 4.2.1 (8c148a)
    Model MC555LL
    Modem Firmware : 06.15.00
    I am currently using this as Unlocked – but tethered by Redsn0w. I want to use it as Untethered, but keeping in mind that NONE of my Apps., and DATA should be affected. I have downloaded “greenpois0n RC6.1 (win)” Please reply me soon, whether loading the above file would affect my DATA & Apps in any way except making it untethered. Thanks in ADVANCE,
    — M0N15H..

  • Arun Thangavel

    Hello Simon,

    Below are my iphone 3G (16GB) details:

    Version: 4.2.1 (8C148)

    Model: MB4967

    Serial Number: 84834TUQY7K

    Wi-Fi Address: 00:23:12:A2:48:87

    Bluetooth: 00:23:12:A2:48:86

    IMEI: 01 171400 496260 4

    ICCID: 8991 4000 0006 2554 1269

    Modem Firmware: 05.15.04

    I got this iPhone couple of years back at “Dubai International Airport” in Duty Free. Its a factory unlocked version. I’m using this iPhone in India right now with the service provider called “AIRTEL”.

    I have been wondering to jailbreak my iPhone for so long time but was really scared on the output. Now that the warranty period also got expired and i believe i can go for “Jail Breaking” now.

    When i bought this iPhone the version was not the same. But using iTunes i have upgraded the version and now i have Version 4.2.1 (8C148).



    Also you have mentioned like:

    “Yes, it’s safe for factory unlocked iPhone. The latest version is RC6.1. Please download it from “www.greenpois0n.com.”





    Best regards,