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 enable value.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Linux | Linux | 6.4 | 6.6.134 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 6.19.12-1 | — |
| Debian 13 | linux | 6.12.85-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Nvidia-BlueField 24.04 LTS | linux-bluefield | 6.8.0-1028.33 | — |
| Ubuntu 26.04 LTS | linux-nvidia | 7.0.0-1006.6 | — |
| Ubuntu 25.10 | linux +8 | No fix yet | — |
| Ubuntu 24.04 LTS | linux | 6.8.0-136.136 | USN-8567-1 |
| Ubuntu 24.04 LTS | linux-aws | 6.8.0-1061.64 | USN-8595-2 |
| Ubuntu 24.04 LTS | linux-azure | 6.8.0-1063.71 | USN-8606-1 |
| Ubuntu 24.04 LTS | linux-azure-fde | 6.8.0-1062.69 | USN-8607-1 |
| Ubuntu 24.04 LTS | linux-gcp | 6.8.0-1064.72 | USN-8567-1 |
| Ubuntu 24.04 LTS | linux-gke | 6.8.0-1059.67 | USN-8567-1 |
| Ubuntu 24.04 LTS | linux-gkeop | 6.8.0-1046.50 | USN-8567-1 |
| Ubuntu 24.04 LTS | linux-ibm | 6.8.0-1061.62 | USN-8574-3 |
| Ubuntu 24.04 LTS | linux-lowlatency | 6.8.0-136.136.2 | USN-8574-2 |
| Ubuntu 24.04 LTS | linux-nvidia | 6.8.0-1059.62 | USN-8596-1 |
| Ubuntu 24.04 LTS | linux-nvidia-lowlatency | 6.8.0-1059.62.1 | USN-8596-1 |
| Ubuntu 24.04 LTS | linux-nvidia-tegra | 6.8.0-1030.31 | USN-8574-3 |
| Ubuntu 24.04 LTS | linux-oracle | 6.8.0-1058.61 | USN-8574-2 |
| Ubuntu 24.04 LTS | linux-raspi | 6.8.0-1061.65 | USN-8665-1 |
| Ubuntu 24.04 LTS | linux-riscv +27 | No fix yet | — |
| Ubuntu 24.04 LTS | linux-vmware | 6.8.0-1008.8 | — |
| Ubuntu 24.04 LTS | linux-xilinx | 6.8.0-1033.34 | USN-8574-3 |
| Ubuntu 22.04 LTS | linux-aws-6.8 | 6.8.0-1061.64~22.04.1 | USN-8595-3 |
| Ubuntu 22.04 LTS | linux-azure-6.8 | 6.8.0-1063.71~22.04.1 | USN-8606-1 |
| Ubuntu 22.04 LTS | linux-azure-fde-6.8 | 6.8.0-1062.69~22.04.1 | USN-8609-1 |
| Ubuntu 22.04 LTS | linux-gcp-6.8 | 6.8.0-1064.72~22.04.1 | USN-8567-1 |
| Ubuntu 22.04 LTS | linux-hwe-6.8 | 6.8.0-136.136~22.04.1 | USN-8619-1 |
| Ubuntu 22.04 LTS | linux-ibm-6.8 | 6.8.0-1061.62~22.04.1 | USN-8574-3 |
| Ubuntu 22.04 LTS | linux-lowlatency-hwe-6.8 | 6.8.0-136.136.2~22.04.1 | USN-8574-2 |
| Ubuntu 22.04 LTS | linux-nvidia-6.8 | 6.8.0-1059.62~22.04.1 | USN-8596-1 |
| Ubuntu 22.04 LTS | linux-oracle-6.8 | 6.8.0-1058.61~22.04.1 | USN-8595-1 |
| Ubuntu 22.04 LTS | linux-riscv +32 | No fix yet | — |
| Ubuntu 22.04 LTS | linux-riscv-6.8 | 6.8.0-136.136~22.04.3 | — |
Show 6 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
| Ubuntu 18.04 LTS | linux-gcp +14 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu Pro Realtime 24.04 LTS | linux-raspi-realtime | 6.8.0-2050.52 | USN-8665-1 |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime | 6.8.1-1056.57 | USN-8567-1 |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime-6.14 +1 | No fix yet | — |
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime-6.8 | 6.8.1-1056.57~22.04.2 | USN-8567-1 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-aws-fips | 6.8.0-1061.64+fips1 | USN-8595-3 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-azure-fips | 6.8.0-1063.71+fips2 | USN-8608-1 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-fips | 6.8.0-136.136+fips2 | USN-8574-2 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-gcp-fips | 6.8.0-1064.72+fips1 | USN-8574-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | kernel-64kb +8 | 6.12.0-160000.37.1 | SUSE-SU-2026:23231-1, SUSE-SU-2026:23221-1 |
| SLES for SAP 16.0 | kernel-default-base | 6.12.0-160000.37.1.160000.2.19 | SUSE-SU-2026:23231-1, SUSE-SU-2026:23221-1 |
| SLES 16.0 | kernel-64kb +8 | 6.12.0-160000.37.1 | SUSE-SU-2026:23237-1, SUSE-SU-2026:23231-1, SUSE-SU-2026:23221-1 |
| SLES 16.0 | kernel-default-base | 6.12.0-160000.37.1.160000.2.19 | SUSE-SU-2026:23231-1, SUSE-SU-2026:23221-1 |
| SLE Micro 6.2 | kernel-default-base | 6.12.0-160000.37.1.160000.2.19 | SUSE-SU-2026:23068-1 |
| SLE Micro 6.2 | kernel-rt +5 | 6.12.0-160000.37.1 | SUSE-SU-2026:23068-1, SUSE-SU-2026:23066-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | kernel-default-base | 6.12.0-160000.37.1.160000.2.19 | openSUSE-SU-2026:21555-1 |
| openSUSE Leap 16.0 | kernel-rt +11 | 6.12.0-160000.37.1 | openSUSE-SU-2026:21555-1 |
Advisories 21
- WID-SEC-2026-1346 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- USN-8574-3 linux-ibm, linux-ibm-6.8, linux-nvidia-tegra, linux-xilinx vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8595-3 linux-aws-6.8, linux-aws-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8574-2 linux-fips, linux-lowlatency, linux-lowlatency-hwe-6.8, linux-oracle vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8596-1 linux-nvidia, linux-nvidia-6.8, linux-nvidia-lowlatency vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8665-1 linux-raspi, linux-raspi-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8608-1 linux-azure-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8574-1 linux-gcp-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8595-2 linux-aws vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8595-1 linux-oracle-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8567-1 linux, linux-gcp, linux-gcp-6.8, linux-gke, linux-gkeop, linux-realtime, linux-realtime-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
- USN-8606-1 linux-azure, linux-azure-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
- USN-8607-1 linux-azure-fde vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
- USN-8619-1 linux-hwe-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
- USN-8609-1 linux-azure-fde-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
- SUSE-SU-2026:23231-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Aug 27, 2026
- SUSE-SU-2026:23237-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Aug 27, 2026
- SUSE-SU-2026:23221-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Aug 27, 2026
- SUSE-SU-2026:23066-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Aug 15, 2026
- SUSE-SU-2026:23068-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Aug 15, 2026
- openSUSE-SU-2026:21555-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Aug 12, 2026
References
- https://git.kernel.org/stable/c/885aa739a07ab45e90dfa997205acec97979ce4e
- https://git.kernel.org/stable/c/ced8b48420eddb1251f93c22dc23fa136490b3cd
- https://git.kernel.org/stable/c/e07237df8538b0ae98dce112e4f6db093d767f80
- https://git.kernel.org/stable/c/f5f6f06d7e6d262026578b59ba7426eb04acce5d
- https://git.kernel.org/stable/c/67c3f99bed6f422ba343d2b70a2eeeccdfd91bef