CVE-2026-64205 (GCVE-0-2026-64205)

Vulnerability from cvelistv5 – Published: 2026-07-20 16:27 – Updated: 2026-07-20 16:27
VLAI
Title
i2c: i801: fix hardware state machine corruption in error path
Summary
In the Linux kernel, the following vulnerability has been resolved: i2c: i801: fix hardware state machine corruption in error path A severe livelock and subsequent Hung Task panic were observed in the i2c-i801 driver during concurrent Fuzzing. The crash is caused by an unconditional hardware register cleanup in the error handling path of i801_access(). When i801_check_pre() fails (e.g., returning -EBUSY because the SMBus controller is actively used by BIOS/ACPI), the kernel does not actually acquire the hardware ownership. However, the code jumps to the 'out' label and executes: iowrite8(SMBHSTSTS_INUSE_STS | STATUS_FLAGS, SMBHSTSTS(priv)); This forcefully clears the INUSE_STS lock and resets the hardware status flags without owning the controller. Doing so interrupts ongoing BIOS/ACPI transactions and totally corrupts the SMBus hardware state machine. Consequently, all subsequent i801_access() calls fail at the pre-check stage, triggering an endless stream of "SMBus is busy, can't use it!" error logs. Over a slow serial console, this printk flood monopolizes the CPU (Console Livelock), starving other processes trying to acquire the mmap_lock down_read semaphore, ultimately triggering the hung task watchdog. Fix this by moving the 'out' label below the hardware register cleanup. If i801_check_pre() fails, we safely bypass the iowrite8() and only release the software locks (pm_runtime and mutex), strictly adhering to the rule of not releasing resources that were never acquired.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1f760b87e54cf56a25ab68f8dc625e339f6e46d5 , < bb5133a7d5f3fe5c387770e25f2e00e682ce11ed (git)
Affected: 1f760b87e54cf56a25ab68f8dc625e339f6e46d5 , < 00904687b9c5527d569d9a1ca72119823e735a61 (git)
Affected: 1f760b87e54cf56a25ab68f8dc625e339f6e46d5 , < 10dd1a736d557e310a77117832874729a0175d57 (git)
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Linux Linux Affected: 6.3
Unaffected: 0 , < 6.3 (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/i2c/busses/i2c-i801.c"
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              "operator": "OR"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ni2c: i801: fix hardware state machine corruption in error path\n\nA severe livelock and subsequent Hung Task panic were observed in the\ni2c-i801 driver during concurrent Fuzzing. The crash is caused by an\nunconditional hardware register cleanup in the error handling path of\ni801_access().\n\nWhen i801_check_pre() fails (e.g., returning -EBUSY because the SMBus\ncontroller is actively used by BIOS/ACPI), the kernel does not actually\nacquire the hardware ownership. However, the code jumps to the \u0027out\u0027\nlabel and executes:\n\n    iowrite8(SMBHSTSTS_INUSE_STS | STATUS_FLAGS, SMBHSTSTS(priv));\n\nThis forcefully clears the INUSE_STS lock and resets the hardware status\nflags without owning the controller. Doing so interrupts ongoing BIOS/ACPI\ntransactions and totally corrupts the SMBus hardware state machine.\n\nConsequently, all subsequent i801_access() calls fail at the pre-check\nstage, triggering an endless stream of \"SMBus is busy, can\u0027t use it!\"\nerror logs. Over a slow serial console, this printk flood monopolizes\nthe CPU (Console Livelock), starving other processes trying to acquire\nthe mmap_lock down_read semaphore, ultimately triggering the hung task\nwatchdog.\n\nFix this by moving the \u0027out\u0027 label below the hardware register cleanup.\nIf i801_check_pre() fails, we safely bypass the iowrite8() and only\nrelease the software locks (pm_runtime and mutex), strictly adhering to\nthe rule of not releasing resources that were never acquired."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-07-20T16:27:53.310Z",
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        "shortName": "Linux"
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    "cveId": "CVE-2026-64205",
    "datePublished": "2026-07-20T16:27:53.310Z",
    "dateReserved": "2026-07-19T15:36:31.769Z",
    "dateUpdated": "2026-07-20T16:27:53.310Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-07-22",
      "epss": "0.00165",
      "percentile": "0.06114"
    },
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      "cve": "CVE-2026-64205",
      "id": "msrc_CVE-2026-64205",
      "initial_release_date": "2026-07-22T01:01:44.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "i2c: i801: fix hardware state machine corruption in error path",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64205.json",
      "version": "1"
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    "redhat_vex": {
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      "cve": "CVE-2026-64205",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: i2c: i801: fix hardware state machine corruption in error path",
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    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.