iOS 4.3 breaks the MobileSubstrate in Cydia after jailbreak. It’s due to the ASLR (Address Space Layout Randomization) implementation in iOS 4.3. Mobile Substrate is an essential base for all the tweaks and hacks available in Cydia.
Saurik has silently updated Mobile Substrate for iOS 4.3 jailbreak. These are the instructions to fix for Mobile Substrate in Cydia after iOS 4.3 jailbreak on iPhone, iPad and iPod touch. Once done! you can install Cydia apps and tweaks of your choice.
Fix MobileSubstrate on iOS 4.3 after Jailbreak
Download this: .deb file.
Navigate to /var/root/Media/
and create a new folder named Cydia and inside Cydia folder, create a folder called AutoInstall (Folder names are Case-Sensitive)
Now copy the downloaded .deb file inside the AutoInstall folder
and reboot your iDevice.