CVE-2025-21773: NULL Pointer Dereference

In the Linux kernel, the following vulnerability has been resolved:

can: etas_es58x: fix potential NULL pointer dereference on udev->serial

The driver assumed that es58x_dev->udev->serial could never be NULL. While this is true on commercially available devices, an attacker could spoof the device identity providing a NULL USB serial number. That would trigger a NULL pointer dereference.

Add a check on es58x_dev->udev->serial before accessing it.