Apple releases iOS 18.3.1 update to patch critical, actively exploited USB security flaw

Apple has started rolling out iOS 18.3.1, a crucial update that fixes a critical security flaw that could allow attackers to gain access to a locked iPhone. The vulnerability, which affects the Accessibility service, could be exploited by physically accessing the device and disabling USB Restricted Mode - a security feature designed to prevent unauthorized access via USB connections. Apple has confirmed that the flaw may have already been used in targeted attacks against individuals.

According to Apple’s release notes, the update patches a flaw that could be used for a physical attack on locked iPhones and iPads. The vulnerability was first discovered by Bill Marczak, a security researcher at The Citizen Lab at The University of Toronto’s Munk School. Apple has credited Marczak for identifying the issue and has advised all users to update their devices immediately.

Understanding the USB Restricted Mode Vulnerability

    •    Introduced in iOS 11.4.1 (2018), USB Restricted Mode blocks unauthorized USB connections unless the iPhone has been unlocked within the past hour.

    •    The new flaw allowed attackers to disable this mode, potentially giving them access to the device via a USB connection.

    •    While the vulnerability required physical access, Apple has warned that it may have been used in highly sophisticated attacks.

The iOS 18.3.1 update is available for all supported iPhones, including the iPhone 16 series and older models going back to the iPhone XS. Users can check for the update by navigating to: Settings > General > Software Update > Install Now