CVE-2026-31740 counter: rz-mtu3-cnt: do not use struct rz_mtu3_channel's dev member
A race condition in the Linux kernel counter driver causes incorrect device pointer assignment, potentially leading to runtime power management errors and system instability.
- 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-2026-31740?
CVE-2026-31740 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:
counter: rz-mtu3-cnt: do not use struct rz_mtu3_channel's dev member
The counter driver can use HW channels 1 and 2, while the PWM driver can use HW channels 0, 1, 2, 3, 4, 6, 7.
The dev member is assigned both by the counter driver and the PWM driver for channels 1 and 2, to their own struct device instance, overwriting the previous value.
The sub-drivers race to assign their own struct device pointer to the same struct rz_mtu3_channel's dev member.
The dev member of struct rz_mtu3_channel is used by the counter sub-driver for runtime PM.
Depending on the probe order of the counter and PWM sub-drivers, the dev member may point to the wrong struct device instance, causing the counter sub-driver to do runtime PM actions on the wrong device.
To fix this, use the parent pointer of the counter, which is assigned during probe to the correct struct device, not the struct device pointer inside the shared struct rz_mtu3_channel.
Which versions are affected by CVE-2026-31740?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31740?
Apply the vendor's patch.
Is CVE-2026-31740 being exploited?
There is no known exploitation of CVE-2026-31740 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-31740, DEBIAN-CVE-2026-31740, GHSA-7cjr-2c82-2wh7, ROOT-OS-UBUNTU-2404-CVE-2026-31740, UBUNTU-CVE-2026-31740.