CVE-2025-40239 net: phy: micrel: always set shared->phydev for LAN8814
A null pointer dereference in the Linux kernel LAN8814 PHY driver causes a kernel crash when handling interrupts, leading to denial of service.
- 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-2025-40239?
CVE-2025-40239 is a vulnerability in Linux, published on 4 Dec 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:
net: phy: micrel: always set shared->phydev for LAN8814
Currently, during the LAN8814 PTP probe shared->phydev is only set if PTP clock gets actually set, otherwise the function will return before setting it.
This is an issue as shared->phydev is unconditionally being used when IRQ is being handled, especially in lan8814_gpio_process_cap and since it was not set it will cause a NULL pointer exception and crash the kernel.
So, simply always set shared->phydev to avoid the NULL pointer exception.
Which versions are affected by CVE-2025-40239?
How do I fix CVE-2025-40239?
Apply the vendor's patch.
Is CVE-2025-40239 being exploited?
There is no known exploitation of CVE-2025-40239 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40239, DEBIAN-CVE-2025-40239, GHSA-g4v3-m8fj-mwj2, UBUNTU-CVE-2025-40239.