CVE-2023-53523 can: gs_usb: fix time stamp counter initialization

What is CVE-2023-53523?

CVE-2023-53523 is a medium-severity vulnerability in Linux kernel, published on 1 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

can: gs_usb: fix time stamp counter initialization

If the gs_usb device driver is unloaded (or unbound) before the interface is shut down, the USB stack first calls the struct usb_driver::disconnect and then the struct net_device_ops::ndo_stop callback.

In gs_usb_disconnect() all pending bulk URBs are killed, i.e. no more RX'ed CAN frames are send from the USB device to the host. Later in gs_can_close() a reset control message is send to each CAN channel to remove the controller from the CAN bus. In this race window the USB device can still receive CAN frames from the bus and internally queue them to be send to the host.

At least in the current version of the candlelight firmware, the queue of received CAN frames is not emptied during the reset command. After loading (or binding) the gs_usb driver, new URBs are submitted during the struct net_device_ops::ndo_open callback and the candlelight firmware starts sending its already queued CAN frames to the host.

However, this scenario was not considered when implementing the hardware timestamp function. The cycle counter/time counter infrastructure is set up (gs_usb_timestamp_init()) after the USBs are submitted, resulting in a NULL pointer dereference if timecounter_cyc2time() (via the call chain: gs_usb_receive_bulk_callback() -> gs_usb_set_timestamp() -> gs_usb_skb_set_timestamp()) is called too early.

Move the gs_usb_timestamp_init() function before the URBs are submitted to fix this problem.

For a comprehensive solution, we need to consider gs_usb devices with more than 1 channel. The cycle counter/time counter infrastructure is setup per channel, but the RX URBs are per device. Once gs_can_open() of _a_ channel has been called, and URBs have been submitted, the gs_usb_receive_bulk_callback() can be called for _all_ available channels, even for channels that are not running, yet. As cycle counter/time counter has not set up, this will again lead to a NULL pointer dereference.

Convert the cycle counter/time counter from a "per channel" to a "per device" functionality. Also set it up, before submitting any URBs to the device.

Further in gs_usb_receive_bulk_callback(), don't process any URBs for not started CAN channels, only resubmit the URB.

Weakness: CWE-476

Which versions are affected by CVE-2023-53523?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2023-53523?

Apply the vendor's patch.

Is CVE-2023-53523 being exploited?

There is no known exploitation of CVE-2023-53523 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2023-53523, DEBIAN-CVE-2023-53523, GHSA-67pq-6gr2-gqmr, ROOT-OS-DEBIAN-12-CVE-2023-53523, UBUNTU-CVE-2023-53523.