iOS 4.3.4 is available for download via iTunes for devices including GSM-based iPhone 4, iPhone 3GS, iPod Touch 4G, iPod Touch 3G, iPad 1, and iPad 2 (Wi-Fi Only, GSM, CDMA). Apple also released an updated version of the firmware, iOS 4.2.9, for CDMA-based iPhone 4.
The iOS 4.3.4 update comes in as Build 8K2, while the iOS 4.2.9 rolls with Build 8E501.
Basically, iOS 4.3.4 and iOS 4.2.9 fix security vulnerability associated with viewing malicious PDF files. However, both of these also patch the exploit used in the latest web-based jailbreaking tool – JailbreakMe 3.0. More of the technical details of this update here and here.
To jailbreakers, note that when you upgrade your device’s firmware to iOS 4.3.4 or iOS 4.2.9, you’ll lose your untethered jailbreak on iOS 4.3.3. If you want to keep your untethered jailbreak on iOS 4.3.3, you need to install PDF Patcher 2 which basically gives you the same effect of iOS 4.3.4 and iOS 4.2.9.
Apple official direct download links of iOS 4.3.4 and iOS 4.2.9 are posted below. You may need to download any of these firmwares compatible with your device for later upgrade.
iPhone 3GS: iPhone2,1_4.3.4_8K2_Restore.ipsw
iPhone 4 (GSM): iPhone3,1_4.3.4_8K2_Restore.ipsw
iPod Touch 3G: iPod3,1_4.3.4_8K2_Restore.ipsw
iPod Touch 4G: iPod4,1_4.3.4_8K2_Restore.ipsw
iPad 1: iPad1,1_4.3.4_8K2_Restore.ipsw
iPad 2 (Wi-Fi): iPad2,1_4.3.4_8K2_Restore.ipsw
iPad 2 (GSM): iPad2,2_4.3.4_8K2_Restore.ipsw
iPad 2 (CDMA): iPad2,3_4.3.4_8K2_Restore.ipsw
iPhone 4 (CDMA) : iPhone3,3_4.2.9_8E501_Restore.ipsw