Apple is leaving some of its older mobile devices unprotected with its latest patch batch.
An iOS 4.3 update, which includes a number of critical security fixes, is incompatible with the still widely used iPhone 3G and older versions of the iPod Touch. The latest version of Apple's mobile software can only be applied on the iPhone 3GSs and later models; the iPod Touch 3rd generation and later models; as well as all versions of the iPad.
Security fixes bundled with the release include protection against the risk posed by maliciously-crafted TIFF image files and security fixes against multiple memory corruption issues in WebKit, the engine behind the Safari browser.
Security firm Sophos warns that the omission of the fixes leaves users of older iPhone and IPod Touches at heightened risk of drive-by download attacks from booby-trapped websites. The latest version of the OS includes tethering functionality and the ability to stream music between devices across home wireless networks, among other functionality improvements.
"There might be a hardware reason why the latest version of the software can't be run on older devices," a Sophos spokesman explained. "Even so, Apple could still release an update for Safari for older devices, the most problematic omission.
"Apple should still produce patches, otherwise security conscious people would have to upgrade."
The handful of malware strains to have infected iPhone devices thus far have only infected jailbroken devices. Although it hasn't yet happened, mobile malware spreading via browser vulnerabilities is a potential threat, Sophos argues.
In related news, Apple also released a new version of its Safari browser for desktops on Wednesday. Safari version 5.0.4 covers a total of 62 security vulnerabilities. Both Windows and Mac users need to update their software.
The vast majority (57 of the 62, by Sophos's count) of the security bugs tackled by the update lend themselves to exploitation simply by tricking a surfer who is running vulnerable versions of the software into visiting a maliciously constructed website, a favourite hacker trick. ®