CVE-2026-90136 (GCVE-0-2026-90136)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:06 – Updated: 2026-09-17 16:06
VLAI
Title
platform/x86/amd/hsmp: Reject negative power cap writes in hwmon
Summary
In the Linux kernel, the following vulnerability has been resolved: platform/x86/amd/hsmp: Reject negative power cap writes in hwmon hsmp_hwmon_write() takes the user-supplied hwmon value as a signed long and assigns "val / MICROWATT_PER_MILLIWATT" to msg.args[0], which is a __u32. MICROWATT_PER_MILLIWATT is an unsigned long, so a negative write to power1_cap (e.g. "echo -1 > power1_cap") is first converted to a huge unsigned value by the division and then stored into the u32 argument. As a result a nonsensical, multi-gigawatt socket power limit is sent to the SMU via HSMP_SET_SOCKET_POWER_LIMIT instead of the write being rejected. Reject negative values with -EINVAL before the conversion. Tested with HSMP enabled: CAP=$(dirname $(grep -l amd_hsmp_hwmon \ /sys/class/hwmon/hwmon*/name | head -1))/power1_cap # negative write echo -1000000 > $CAP ; echo "ret=$?" # valid positive write must still work echo 400000000 > $CAP ; echo "ret=$?" Before: # echo -1000000 > $CAP ; echo "ret=$?" ret=0 <- accepted; bogus limit sent to SMU # echo 400000000 > $CAP ; echo "ret=$?" ret=0 After: # echo -1000000 > $CAP ; echo "ret=$?" bash: echo: write error: Invalid argument ret=1 <- rejected with -EINVAL # echo 400000000 > $CAP ; echo "ret=$?" ret=0 <- valid write still works
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 92c025db52bb94a032eb3d473bb81e62c19ddbd3 , < 2c09cadec116eba3fdbcb5d8d8641f6777d4a11f (git)
Affected: 92c025db52bb94a032eb3d473bb81e62c19ddbd3 , < 1b0a3d915320f1600e5ff43f8bc21b73118480b8 (git)
Affected: 92c025db52bb94a032eb3d473bb81e62c19ddbd3 , < 3921bb8635ff2836622df1cdf3194d4f3c1835a4 (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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        {
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          "product": "Linux",
          "programFiles": [
            "drivers/platform/x86/amd/hsmp/hwmon.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "versionType": "git"
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          "versions": [
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              "version": "0",
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              "version": "6.18.52",
              "versionType": "semver"
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              "status": "unaffected",
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                  "versionEndExcluding": "7.2.6",
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                  "vulnerable": true
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                  "versionStartIncluding": "6.16",
                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nplatform/x86/amd/hsmp: Reject negative power cap writes in hwmon\n\nhsmp_hwmon_write() takes the user-supplied hwmon value as a signed long\nand assigns \"val / MICROWATT_PER_MILLIWATT\" to msg.args[0], which is a\n__u32.  MICROWATT_PER_MILLIWATT is an unsigned long, so a negative write\nto power1_cap (e.g. \"echo -1 \u003e power1_cap\") is first converted to a huge\nunsigned value by the division and then stored into the u32 argument.\n\nAs a result a nonsensical, multi-gigawatt socket power limit is sent to\nthe SMU via HSMP_SET_SOCKET_POWER_LIMIT instead of the write being\nrejected.\n\nReject negative values with -EINVAL before the conversion.\n\nTested with HSMP enabled:\n\n  CAP=$(dirname $(grep -l amd_hsmp_hwmon \\\n        /sys/class/hwmon/hwmon*/name | head -1))/power1_cap\n\n  # negative write\n  echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  # valid positive write must still work\n  echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n\nBefore:\n  # echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0                             \u003c- accepted; bogus limit sent to SMU\n  # echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0\n\nAfter:\n  # echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  bash: echo: write error: Invalid argument\n  ret=1                             \u003c- rejected with -EINVAL\n  # echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0                             \u003c- valid write still works"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T16:06:35.190Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
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          "url": "https://git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f"
        },
        {
          "url": "https://git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8"
        },
        {
          "url": "https://git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4"
        }
      ],
      "title": "platform/x86/amd/hsmp: Reject negative power cap writes in hwmon",
      "x_generator": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90136",
    "datePublished": "2026-09-17T16:06:35.190Z",
    "dateReserved": "2026-09-11T19:38:34.788Z",
    "dateUpdated": "2026-09-17T16:06:35.190Z",
    "state": "PUBLISHED"
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-90136",
      "date": "2026-09-25",
      "epss": "0.00206",
      "percentile": "0.09504"
    },
    "nvd": {
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          {
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                "product": "Linux",
                "programFiles": [
                  "drivers/platform/x86/amd/hsmp/hwmon.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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                    "versionType": "git"
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                "programFiles": [
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                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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                "versions": [
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                    "versionType": "semver"
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                    "status": "unaffected",
                    "version": "7.2.6",
                    "versionType": "semver"
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                    "versionType": "original_commit_for_fix"
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              }
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nplatform/x86/amd/hsmp: Reject negative power cap writes in hwmon\n\nhsmp_hwmon_write() takes the user-supplied hwmon value as a signed long\nand assigns \"val / MICROWATT_PER_MILLIWATT\" to msg.args[0], which is a\n__u32.  MICROWATT_PER_MILLIWATT is an unsigned long, so a negative write\nto power1_cap (e.g. \"echo -1 \u003e power1_cap\") is first converted to a huge\nunsigned value by the division and then stored into the u32 argument.\n\nAs a result a nonsensical, multi-gigawatt socket power limit is sent to\nthe SMU via HSMP_SET_SOCKET_POWER_LIMIT instead of the write being\nrejected.\n\nReject negative values with -EINVAL before the conversion.\n\nTested with HSMP enabled:\n\n  CAP=$(dirname $(grep -l amd_hsmp_hwmon \\\n        /sys/class/hwmon/hwmon*/name | head -1))/power1_cap\n\n  # negative write\n  echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  # valid positive write must still work\n  echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n\nBefore:\n  # echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0                             \u003c- accepted; bogus limit sent to SMU\n  # echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0\n\nAfter:\n  # echo -1000000 \u003e $CAP ; echo \"ret=$?\"\n  bash: echo: write error: Invalid argument\n  ret=1                             \u003c- rejected with -EINVAL\n  # echo 400000000 \u003e $CAP ; echo \"ret=$?\"\n  ret=0                             \u003c- valid write still works"
          }
        ],
        "id": "CVE-2026-90136",
        "lastModified": "2026-09-17T17:17:06.173",
        "metrics": {},
        "published": "2026-09-17T17:17:06.173",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/1b0a3d915320f1600e5ff43f8bc21b73118480b8"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/2c09cadec116eba3fdbcb5d8d8641f6777d4a11f"
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            "url": "https://git.kernel.org/stable/c/3921bb8635ff2836622df1cdf3194d4f3c1835a4"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "suse_vex": {
      "aggregate_severity": "low",
      "current_release_date": "2026-09-21T16:32:33Z",
      "cve": "CVE-2026-90136",
      "id": "CVE-2026-90136",
      "initial_release_date": "2026-09-18T00:20:52Z",
      "product_status:known_not_affected": "347",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-90136",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-90136.json",
      "version": "4"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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