CVE-2025-21776

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

USB: hub: Ignore non-compliant devices with too many configs or interfaces

Robert Morris created a test program which can cause usb_hub_to_struct_hub() to dereference a NULL or inappropriate pointer:

Oops: general protection fault, probably for non-canonical address 0xcccccccccccccccc: 0000 [#1] SMP DEBUG_PAGEALLOC PTI CPU: 7 UID: 0 PID: 117 Comm: kworker/7:1 Not tainted 6.13.0-rc3-00017-gf44d154d6e3d #14 Hardware name: FreeBSD BHYVE/BHYVE, BIOS 14.0 10/17/2021 Workqueue: usb_hub_wq hub_event RIP: 0010:usb_hub_adjust_deviceremovable+0x78/0x110 … Call Trace: ? die_addr+0x31/0x80 ? exc_general_protection+0x1b4/0x3c0 ? asm_exc_general_protection+0x26/0x30 ? usb_hub_adjust_deviceremovable+0x78/0x110 hub_probe+0x7c7/0xab0 usb_probe_interface+0x14b/0x350 really_probe+0xd0/0x2d0 ? __pfx___device_attach_driver+0x10/0x10 __driver_probe_device+0x6e/0x110 driver_probe_device+0x1a/0x90 __device_attach_driver+0x7e/0xc0 bus_for_each_drv+0x7f/0xd0 __device_attach+0xaa/0x1a0 bus_probe_device+0x8b/0xa0 device_add+0x62e/0x810 usb_set_configuration+0x65d/0x990 usb_generic_driver_probe+0x4b/0x70 usb_probe_device+0x36/0xd0

The cause of this error is that the device has two interfaces, and the hub driver binds to interface 1 instead of interface 0, which is where usb_hub_to_struct_hub() looks.

We can prevent the problem from occurring by refusing to accept hub devices that violate the USB spec by having more than one configuration or interface.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/2240fed37afbcdb5e8b627bc7ad986891100e05d
• https://git.kernel.org/stable/c/49f077106fa07919a6a6dda99bb490dd1d1a8218
• https://git.kernel.org/stable/c/5b9778e1fe715700993ce436c152dc3b7df0b490
• https://git.kernel.org/stable/c/62d8f4c5454dd39aded4f343720d1c5a1803cfef
• https://git.kernel.org/stable/c/c3720b04df84b5459050ae4e03ec7d545652f897
• https://git.kernel.org/stable/c/d343fe0fad5c1d689775f2dda24a85ce98e29566
• https://git.kernel.org/stable/c/d3a67adb365cdfdac4620daf38a82e57ca45806c
• https://git.kernel.org/stable/c/e905a0fca7bff0855d312c16f71e60e1773b393e