CVE-2026-64191 (GCVE-0-2026-64191)

Vulnerability from cvelistv5 – Published: 2026-07-20 16:27 – Updated: 2026-08-05 12:39
VLAI
Title
i2c: stub: Reject I2C block transfers with invalid length
Summary
In the Linux kernel, the following vulnerability has been resolved: i2c: stub: Reject I2C block transfers with invalid length The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter. A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer: BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223) Read of size 1 at addr ffff88800abcfd92 by task exploit/81 Call Trace: <TASK> stub_xfer (drivers/i2c/i2c-stub.c:223) __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593) i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536) i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391) i2cdev_ioctl (drivers/i2c/i2c-dev.c:478) __x64_sys_ioctl (fs/ioctl.c:583) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) </TASK> The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not. Fix by rejecting transfers with data->block[0] == 0 or data->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 7e9072dbd5f2f17934751873450d2c22080ead80 (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 21e87f336ac6303fed54a69b1d0d79a23b25c8d0 (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 4bd8635f28c135a08aac6badcd7d9b5cdb34335f (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 5f4d2bd028ebb6e4c09a9d64842546022321d4a7 (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 0526931b16e5a118d367b7bfce7d797e63f7ac69 (git)
Affected: 4710317891e4824ce1510a6b5066abbd3e917750 , < 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e (git)
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Linux Linux Affected: 2.6.33
Unaffected: 0 , < 2.6.33 (semver)
Unaffected: 5.10.260 , ≤ 5.10.* (semver)
Unaffected: 5.15.211 , ≤ 5.15.* (semver)
Unaffected: 6.1.177 , ≤ 6.1.* (semver)
Unaffected: 6.6.144 , ≤ 6.6.* (semver)
Unaffected: 6.12.95 , ≤ 6.12.* (semver)
Unaffected: 6.18.37 , ≤ 6.18.* (semver)
Unaffected: 7.0.14 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "C8AD3BC8-C843-423C-B9DB-CB52F67F578E",
                    "versionEndExcluding": "6.6.144",
                    "versionStartIncluding": "6.2",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "E08ACB05-518A-4D61-A6C4-268D1BB6BF46",
                    "versionEndExcluding": "6.18.37",
                    "versionStartIncluding": "6.13",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "6241DF06-E6F3-4B61-B5A2-A60F2AE5B982",
                    "versionEndExcluding": "7.0.14",
                    "versionStartIncluding": "6.19",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*",
                    "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*",
                    "matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ni2c: stub: Reject I2C block transfers with invalid length\n\nThe I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data-\u003eblock[0]\nas the transfer length. The existing check only clamps it to avoid\noverrunning the chip-\u003ewords[256] register array, but does not validate\nit against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union\ni2c_smbus_data.block buffer (34 bytes total). The driver is a\ndevelopment/test tool (CONFIG_I2C_STUB=m, not built by default)\nthat must be loaded with a chip_addr= parameter.\n\nA local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl\nwith I2C_SMBUS_I2C_BLOCK_DATA and data-\u003eblock[0] \u003e 32, causing\nstub_xfer() to read or write past the end of the union\ni2c_smbus_data.block buffer:\n\n BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223)\n Read of size 1 at addr ffff88800abcfd92 by task exploit/81\n Call Trace:\n  \u003cTASK\u003e\n  stub_xfer (drivers/i2c/i2c-stub.c:223)\n  __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593)\n  i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536)\n  i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391)\n  i2cdev_ioctl (drivers/i2c/i2c-dev.c:478)\n  __x64_sys_ioctl (fs/ioctl.c:583)\n  do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n  \u003c/TASK\u003e\n\nThe bug exists because i2c-stub implements .smbus_xfer directly,\nbypassing the I2C_SMBUS_BLOCK_MAX validation in\ni2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same\nfunction correctly validates against I2C_SMBUS_BLOCK_MAX, but the\nI2C_SMBUS_I2C_BLOCK_DATA case does not.\n\nFix by rejecting transfers with data-\u003eblock[0] == 0 or\ndata-\u003eblock[0] \u003e I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with\nboth the I2C_SMBUS_BLOCK_DATA case in the same function and the\nI2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated()."
          }
        ],
        "id": "CVE-2026-64191",
        "lastModified": "2026-08-11T19:05:37.520",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-20T17:18:22.217",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-125"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-09T07:35:56+00:00",
      "cve": "CVE-2026-64191",
      "id": "CVE-2026-64191",
      "initial_release_date": "2026-07-20T00:00:00+00:00",
      "product_status:fixed": "930",
      "product_status:known_affected": "126",
      "product_status:known_not_affected": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: i2c: stub: Reject I2C block transfers with invalid length",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64191.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-18T00:43:00Z",
      "cve": "CVE-2026-64191",
      "id": "CVE-2026-64191",
      "initial_release_date": "2026-07-21T12:58:02Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "675",
      "product_status:known_not_affected": "46",
      "product_status:recommended": "311",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64191",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64191.json",
      "version": "13"
    }
  }
}



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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

Author Source Type Date Other

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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.