i2c: stub: Reject I2C block transfers with invalid length

{
  "id": "95980b3ffbbbca52da5a52f8a5f23549673b7b990258e951a0fe76fe466a0a40",
  "url": "https://osv.dev/vulnerability/CVE-2026-64191",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "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: 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) 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 ",
    "evidence": "osv:CVE-2026-64191",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.260",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.211",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.177",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.144",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.95",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.37",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.0.14",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-64191",
      "aliases": [
        "CVE-2026-64191"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "4710317891e4824ce1510a6b5066abbd3e917750"
                },
                {
                  "fixed": "7e9072dbd5f2f17934751873450d2c22080ead80"
                },
                {
                  "fixed": "21e87f336ac6303fed54a69b1d0d79a23b25c8d0"
                },
                {
                  "fixed": "3fd225f3e4cd67ec8ddab1afed9da03c7c43537c"
                },
                {
                  "fixed": "1c4ffe6b4f04365485ed58d64c9bb86b46fc9037"
                },
                {
                  "fixed": "4bd8635f28c135a08aac6badcd7d9b5cdb34335f"
                },
                {
                  "fixed": "5f4d2bd028ebb6e4c09a9d64842546022321d4a7"
                },
                {
                  "fixed": "0526931b16e5a118d367b7bfce7d797e63f7ac69"
                },
                {
                  "fixed": "6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64191.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "2.6.33"
                },
                {
                  "fixed": "5.10.260"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.211"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.177"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.144"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.95"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.37"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.0.14"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64191.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.908596542Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69",
        "https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037",
        "https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0",
        "https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c",
        "https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f",
        "https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7",
        "https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e",
        "https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64191.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64191",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64191.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64191",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 506390,
  "published_at": "2026-07-20T16:27:51.12+00:00"
}