Notcom, the developer behind TinyUmbrella has added the Verizon iPhone 4 support to TinyUmbrella and has released a new version (4.21.08) of the software. But the TinyUmbrella 4.21.08 version is in the beta state. The software is available for both Windows and Mac OS X.
This is what he wrote in his blog :
TinyUmbrella has been updated to support iPhone 4 CDMA aka Verizon. Note that since I do not have a Verizon iPhone 4, support is BETA.
TinyUmbrella 4.21.08 supports the SHSH blobs saving of Verizon iPhone 4 which is on iOS 4.2.6 firmware.
Download TinyUmbrella 4.21.08 for Mac OS X from here
Download TinyUmbrella 4.21.08 for Windows from here