CVE-2026-31728 usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop
A race condition in the Linux kernel USB gadget driver causes a NULL pointer dereference and hardlockup, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31728?
CVE-2026-31728 is a medium-severity vulnerability in Linux kernel, published on 1 May 2026. 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:
usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop
A race condition between gether_disconnect() and eth_stop() leads to a NULL pointer dereference. Specifically, if eth_stop() is triggered concurrently while gether_disconnect() is tearing down the endpoints, eth_stop() attempts to access the cleared endpoint descriptor, causing the following NPE:
Unable to handle kernel NULL pointer dereference Call trace: __dwc3_gadget_ep_enable+0x60/0x788 dwc3_gadget_ep_enable+0x70/0xe4 usb_ep_enable+0x60/0x15c eth_stop+0xb8/0x108
Because eth_stop() crashes while holding the dev->lock, the thread running gether_disconnect() fails to acquire the same lock and spins forever, resulting in a hardlockup:
Core - Debugging Information for Hardlockup core(7) Call trace: queued_spin_lock_slowpath+0x94/0x488 _raw_spin_lock+0x64/0x6c gether_disconnect+0x19c/0x1e8 ncm_set_alt+0x68/0x1a0 composite_setup+0x6a0/0xc50
The root cause is that the clearing of dev->port_usb in gether_disconnect() is delayed until the end of the function.
Move the clearing of dev->port_usb to the very beginning of gether_disconnect() while holding dev->lock. This cuts off the link immediately, ensuring eth_stop() will see dev->port_usb as NULL and safely bail out.
Weakness: CWE-362
Which versions are affected by CVE-2026-31728?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31728?
Apply the vendor's patch.
Is CVE-2026-31728 being exploited?
There is no known exploitation of CVE-2026-31728 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-31728, DEBIAN-CVE-2026-31728, GHSA-fhp6-cw2v-3rqj, ROOT-OS-DEBIAN-11-CVE-2026-31728, ROOT-OS-UBUNTU-2204-CVE-2026-31728, ROOT-OS-UBUNTU-2404-CVE-2026-31728 and 1 more.