September 23, 2021

Security researcher Park Minchan discovered a bug in Apple’s macOS devices that allows remote attackers to execute arbitrary commands on users’ devices.

This is done by shortcut files that have the inetloc extension, which is able to embed commands inside.

While internet shortcuts are present in both Windows and macOS systems, the vulnerability mainly affects users of macOS Big Sur and earlier versions, especially those using a native email client such as the “Mail” app.

Minchan clarified: “A vulnerability in the way macOS processes inetloc files causes it to run commands embedded inside, the commands it runs can be local to the macOS allowing the execution of arbitrary commands by the user without any warning/prompts. Originally, inetloc files are shortcuts to an internet location, such as an RSS feed or a telnet location; and contain the server address and possibly a username and password for SSH and telnet connections; can be created by typing a URL in a text editor and dragging the text to the Desktop.”

The vulnerability is caused by the inclusion of the “file://” URL which is used to retrieve files from a user’s computer system.

Therefore, a user opening a local file on their own computer with the Chrome or Safari web browser automatically creates the corresponding file:// location in the address bar, which makes it easy to design internet shortcuts or inetloc files to point to “file:/ /,” as opposed to HTTP files.

While Minchan acknowledged the fact that Apple had blocked the bug in the newer version of macOS from Big Sur, he explained that the tech company had conducted a case review that allowed File:// or fIIe:// to bypass the audit.

For more information, read the original story in Ars Technica.