In squashing software bugs, you inevitably introduce new ones—that’s a fact of life. According to a thread on Reddit, Apple’s recent OS X security update has inadvertently disabled the Ethernet port for some owners of Apple’s all-in-one desktop and the MacBook Pro notebook.
Making matter worse is the fact that Apple pushed this security update via the silent updating mechanism, according to a poster on Reddit who probably enabled the option in System Preferences → App Store that prompts OS X to automatically install system data files and security updates.
The security update in question is labeled “031-51913 Incompatible Kernel Extension Configuration Data 3.28.1” and it apparently blacklists the Broadcom BCM5701 driver.
Apple has since pulled the update from its servers.
People who have already installed the update and cannot use their Mac’s Ethernet port as a result, forcing them to use Wi-Fi to get online, should boot into OS X Recovery Mode and restore the following folder from a Time Machine backup or another Mac running the same OS X version:
“If this stays broken until Monday there are going to be a lot of pissed off Mac users come next week,” wrote the poster.
If your Mac is affected, the Ethernet Cards sub-section under the Hardware heading in the System Information window (Apple menu → About This Mac → System Report will read “This computer does not appear to have any PCI Ethernet cards installed.”
Until Apple provides a fix, affected users can do a basic reinstallation of OS X using the El Capitan installer on a USB thumb drive or reinstall OS X in Recovery Mode.
Reinstalling OS X won’t delete your personal files or settings.
“Generally you don’t need to erase your startup disk to reinstall OS X,” explains Apple. “The OS X Installer is designed to allow you to perform an install in place over the same version or earlier versions of OS X.”
We have reached out to Apple for commentary on the situation and will update this article if we receive their official response.