CVE-2026-31741

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

counter: rz-mtu3-cnt: prevent counter from being toggled multiple times

Runtime PM counter is incremented / decremented each time the sysfs

enable file is written to.

If user writes 0 to the sysfs enable file multiple times, runtime PM

usage count underflows, generating the following message.

rz-mtu3-counter rz-mtu3-counter.0: Runtime PM usage count underflow!

At the same time, hardware registers end up being accessed with clocks

off in rz_mtu3_terminate_counter() to disable an already disabled

channel.

If user writes 1 to the sysfs enable file multiple times, runtime PM

usage count will be incremented each time, requiring the same number of

0 writes to get it back to 0.

If user writes 0 to the sysfs enable file while PWM is in progress, PWM

is stopped without counter being the owner of the underlying MTU3

channel.

Check against the cached count_is_enabled value and exit if the user

is trying to set the same en

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References