CVE-2025-21773

What it actually does

The driver dereferences a USB serial number pointer without validation, allowing a NULL value from a spoofed device identity to trigger a kernel NULL pointer dereference.

Why it matters to the business

Systems relying on the affected USB CAN hardware face potential kernel crashes and denial of service; the issue remains unexploited in known campaigns despite the age of the disclosure and similar kernel privilege issues observed in the ecosystem.

How an attack unfolds

An attacker physically or virtually presents a spoofed USB device that supplies a NULL serial number; the driver code path that assumes a valid serial value then performs an unchecked dereference, resulting in a crash. No named threat actors have been observed chaining this specific flaw, though related kernel privilege-escalation techniques appear in other reported cases.

How to fix it

Update the Linux kernel to the commit 1590667a60753ee5a54871f2840ceefd4a7831fa or later; for django-rest-framework deployments update to version 3.9.1. Rebuild and reboot affected systems after applying the fix.

How to confirm the fix worked

Confirm the running kernel contains commit 1590667a60753ee5a54871f2840ceefd4a7831fa; attempt to load the driver with a device presenting a NULL serial and verify no panic occurs.

Typical attack path

1. Attach or emulate a USB device reporting a NULL serial number to the etas_es58x driver
2. Trigger the code path that reads es58x_dev->udev->serial without a prior NULL check
3. Cause the kernel to dereference the NULL pointer and panic

How to detect it

Review kernel logs for NULL pointer dereference oops messages originating from the etas_es58x driver; inspect USB device enumeration events that report missing serial numbers.

What your security team should do

• Prioritize kernel updates on any hosts exposing the etas_es58x driver to untrusted USB devices
• Monitor for similar NULL-dereference patterns in other USB CAN drivers
• Restrict physical USB access where possible until patches are deployed