CVE-2026-31741

About vulnerability

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 enable value. A flaw was found in the Linux kernel’s rz-mtu3-cnt counter module. A local user can exploit this by repeatedly writing ‘0’ to the sysfs enable file, which causes the runtime Power Management (PM) usage count to underflow. This can lead to attempts to access hardware registers with their clocks off, potentially causing system instability or a denial of service (DoS). Additionally, repeated writes of ‘1’ can cause the usage count to increment indefinitely, requiring an equal number of ‘0’ writes to reset it.

Live-patch status from KernelCare for each operating system.