Recent OS X security update breaks Ethernet for most Macs

Did your Mac’s Ethernet port mysteriously stop working recently? If so, you could have fallen afoul of a nasty bug that was introduced in a recent OS X security update. Here’s how to fix it.

As pointed out on Reddit, a recent OS X security update called “031–51913 Incompatible Kernel Extension Configuration Data 3.28.1” blacklists the BCM5701 driver.

The only problem? Almost every Mac with an Ethernet port depends on that driver. And while Apple has since pulled that update from their servers, there’s a chance you might have been afflicted.