CVE-2026-98796 net: ethernet: mtk_eth_soc: allocate dummy netdev sooner
A race condition in the MediaTek Ethernet driver causes a null pointer dereference and denial of service if an interface is brought up during probe.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98796?
CVE-2026-98796 is a vulnerability in Linux, published on 18 Oct 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:
net: ethernet: mtk_eth_soc: allocate dummy netdev sooner
The RX rings and the shared NAPI are carried by an internal "dummy" netdev (eth->dummy_dev). mtk_probe() creates that dummy device, and adds the shared tx/rx NAPI to it, only after the MAC netdevs have been registered. That order has been there since the MT7623 support was added and leaves a window in which the netdevs are visible to the network core before the shared NAPI and the dummy device exist.
If anything brings the first netdev up during that window (e.g. netifd opening the WAN link the instant the interface is registered), the first-open path runs without them. On NETSYS v2 and later SoCs mtk_rx_alloc() -> __xdp_rxq_info_reg() then dereferences eth->dummy_dev == NULL:
WARNING: CPU: ... Missing net_device from driver
in net/core/xdp.c and mtk_open() fails with -ENODEV. On NETSYS v1 SoCs (MT7621/MT7622/MT7623/MT7629) there is no page pool, so the same open instead calls napi_enable() on a napi_struct that netif_napi_add() has not initialised yet and dereferences a NULL napi->dev.
Allocate the dummy netdev and add the shared tx/rx NAPI to it before the register_netdev() loop. Both the dummy-allocation failure and a register_netdev() failure now unwind through mtk_unreg_dev(), which unregisters the net_device notifiers and the netdevs registered so far, stopping a concurrently-opened netdev (ndo_stop) and its NAPI before the dummy carrier is freed.
A netdev that opened during the window can also have queued the frame-engine reset worker (via the tx watchdog or phylink), so the probe error path now cancels eth->pending_work before freeing the shared state, as mtk_cleanup() already does on remove.
Which versions are affected by CVE-2026-98796?
How do I fix CVE-2026-98796?
Apply the vendor's patch.
Is CVE-2026-98796 being exploited?
There is no known exploitation of CVE-2026-98796 in the wild and no public exploit code.
Sources
Also known as AZL-109079, BELL-CVE-2026-98796, DEBIAN-CVE-2026-98796, GHSA-vc65-jh42-gc6g, UBUNTU-CVE-2026-98796.