CVE-2026-64496 (GCVE-0-2026-64496)
Vulnerability from cvelistv5
Published
2026-07-25 08:51
Modified
2026-08-17 04:56
Severity ?
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: iio: event: Fix event FIFO reset race `iio_event_getfd()` creates the event file descriptor with `anon_inode_getfd()`, which allocates a new fd, creates the anonymous file and installs it in the process fd table before returning to the caller. The IIO code resets the event FIFO after `anon_inode_getfd()` has returned, but before `IIO_GET_EVENT_FD_IOCTL` has copied the fd number to userspace. But since fd tables are shared between threads, another thread can guess the newly allocated fd number and issue a `read()` on it as soon as the fd has been installed. This means the `kfifo_to_user()` in `iio_event_chrdev_read()` can run in parallel with the `kfifo_reset_out()` in `iio_event_getfd()`. The kfifo documentation says that `kfifo_reset_out()` is only safe when it is called from the reader thread and there is only one concurrent reader. Otherwise it is dangerous and must be handled in the same way as `kfifo_reset()`. If that happens, `kfifo_to_user()` can advance the FIFO `out` index based on state from before the reset, after the reset has already moved the `out` index to the current `in` index. That can leave the FIFO with an `out` index past the `in` index. A later `read()` can then see an underflowed FIFO length and copy more data than the event FIFO buffer contains. This can result in an out-of-bounds read and leak adjacent kernel memory to userspace. Move the FIFO reset before `anon_inode_getfd()`. At that point the event fd is marked busy, but the new fd has not been installed yet, so userspace cannot access it while the FIFO is reset.
References
Impacted products
Vendor Product Version
Linux Linux Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
Version: b91accafbb1031b80d22ad83576877ff2f8b4774
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{
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          "product": "Linux",
          "programFiles": [
            "drivers/iio/industrialio-event.c"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niio: event: Fix event FIFO reset race\n\n`iio_event_getfd()` creates the event file descriptor with\n`anon_inode_getfd()`, which allocates a new fd, creates the anonymous\nfile and installs it in the process fd table before returning to the\ncaller.\n\nThe IIO code resets the event FIFO after `anon_inode_getfd()` has returned,\nbut before `IIO_GET_EVENT_FD_IOCTL` has copied the fd number to userspace.\nBut since fd tables are shared between threads, another thread can guess\nthe newly allocated fd number and issue a `read()` on it as soon as the fd\nhas been installed.\n\nThis means the `kfifo_to_user()` in `iio_event_chrdev_read()` can run in\nparallel with the `kfifo_reset_out()` in `iio_event_getfd()`.\n\nThe kfifo documentation says that `kfifo_reset_out()` is only safe when it\nis called from the reader thread and there is only one concurrent reader.\nOtherwise it is dangerous and must be handled in the same way as\n`kfifo_reset()`.\n\nIf that happens, `kfifo_to_user()` can advance the FIFO `out` index based\non state from before the reset, after the reset has already moved the `out`\nindex to the current `in` index. That can leave the FIFO with an `out`\nindex past the `in` index. A later `read()` can then see an underflowed\nFIFO length and copy more data than the event FIFO buffer contains. This\ncan result in an out-of-bounds read and leak adjacent kernel memory to\nuserspace.\n\nMove the FIFO reset before `anon_inode_getfd()`. At that point the event fd is\nmarked busy, but the new fd has not been installed yet, so userspace cannot\naccess it while the FIFO is reset."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation uses local open(), ioctl(), and read() operations on /dev/iio:deviceX; no network-reachable path exists.\nAC:L - The attacker controls both racing threads and can predict the lowest available event fd, repeatedly race its installation, and stall the read using a userspace page fault.\nPR:L - The kernel path has no capability or authentication check; an ordinary user granted device-node access can invoke the vulnerable ioctl and read operations.\nUI:N - No victim action is required, and supported IIO drivers can generate events automatically through sensor interrupts.\nS:U - The vulnerability affects the kernel hosting the attacking process and does not inherently cross a VM, IOMMU, or separate security-authority boundary.\nC:H - The underflowed FIFO length permits an attacker-sized out-of-bounds read beyond the 256-byte event buffer, exposing adjacent kernel heap memory and potentially sensitive pointers or data.\nI:N - The path copies kernel data to userspace and corrupts only the FIFO read index; masked FIFO accesses provide no out-of-bounds write or control-flow modification primitive.\nA:H - An oversized read crossing the containing slab object triggers BUG() with hardened usercopy, causing a kernel oops or panic and allowing repeated denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:56:44.840Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/9dc84ba4be5bbeb29ee49efe6cea2cb32c461424"
        },
        {
          "url": "https://git.kernel.org/stable/c/d16a702ca7d29c0b7a9b509339d1b044a1cadb32"
        },
        {
          "url": "https://git.kernel.org/stable/c/a13ef1adbc62085b21b546b07b0be7e2fbf52150"
        },
        {
          "url": "https://git.kernel.org/stable/c/0d4a646d7f87ea3625fafe387043fddc6a2f5e7f"
        },
        {
          "url": "https://git.kernel.org/stable/c/72c6aa8e0d74eab91b8694cde97dec088c248fee"
        },
        {
          "url": "https://git.kernel.org/stable/c/9edefd4c56bee3fe331e0355d1f10a533134999d"
        },
        {
          "url": "https://git.kernel.org/stable/c/f187dc5a4c4846ffa07d9bda6e760837ed005574"
        },
        {
          "url": "https://git.kernel.org/stable/c/af791d295737ea6b6ff2c8d8488462a49c14af01"
        }
      ],
      "title": "iio: event: Fix event FIFO reset race",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64496",
    "datePublished": "2026-07-25T08:51:53.194Z",
    "dateReserved": "2026-07-19T15:36:31.792Z",
    "dateUpdated": "2026-08-17T04:56:44.840Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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