Even though a CDMA version of the iPhone 4 that has been specifically engineered for the Verizon Wireless network won’t land on store shelves until next Thursday, already an iOS firmware update has surfaced on Apple’s servers.

The standalone download is available now, although the chance is it won’t appear as an automatic update in iTunes until February 10, when the Verizon iPhone is scheduled to officially launch.

Carrying version number 4.2.6, the download weighs in at 625MB, which is 28MB extra over the most recent iOS release for GSM iPhone 4. Other than the CDMA circuitry and a slightly redesigned antennae, the iPhone 4 is a carbon-copy replica of its AT&T counterpart hardware-wise.

That an incremental update to iOS 4.2.5 appeared on Apple’s servers would suggest last-minute bug squashing in the run-up to the launch. When the nation’s leading carrier took the wraps off the handset last month, we learned it would run iOS 4.2.5 that contains software support for its new CDMA chip, in addition to the WiFi tethering feature dubbed Personal Hotspot.

As the name suggests, Personal Hotspot lets you share your cellular 3G service with up to five WiFi devices connecting to your iPhone 4 which doubles as a wireless base station. Verizon has been offering a similar feature on its flagship Android phones for some time. Here’s to the hoping that iOS 4.3 will be a universal release for both CDMA and GSM iPhones, in addition to iPod touches as well. Nothing beats simplicity.