CVE-2026-99254

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. task_work_run() only returns when it finds the list empty. If the rings are released from inside the cancellation, because requests of other rings held the last references to their files, up to 64 work items keep sending callbacks to the one task which is running them. It never finds the list empty, never gets back to the cancellation, the nodes stay, and so it goes on: a task with 60 pairs of rings which poll each other ran 280000 callbacks in 5 seconds, 20 seconds after exit_group(). It ends when all the senders happen to be late at the same time. Until then the task keeps a CPU and the work items busy. An exiting task can't be killed meanwhile. execve() cancels the requests in the same way, so a live task can get stuck there as well, for minutes. If it takes more than five, the work items run into the WARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No privilege is needed for any of this. If the callback has met a task in cancellation, wait a little before it is sent again. Nobody has to wake the work item up for that: either the node is gone by then, or it is the turn of the next round.

Severity

Not scored

CVSS score

Not available

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-11-03 12:17:32.137000

Last modified

2026-11-03 12:17:32.137000

View original CVE JSON

{
  "id": "CVE-2026-99254",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-11-03T12:17:32.137",
  "lastModified": "2026-11-03T12:17:32.137",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: don't flood a cancelling task with task_work\n\nio_ring_exit_work() asks each task which has used the ring to remove its\ntctx node, by task_work, and repeats that until the list is empty.\nio_tctx_exit_cb() doesn't touch the node while the task is in\nio_uring_cancel_generic(), which removes all the nodes at its end. So the\nwork item queues the callback again as soon as it has completed, for\nnothing.\n\nThat is more than a waste of time. task_work_run() only returns when it\nfinds the list empty. If the rings are released from inside the\ncancellation, because requests of other rings held the last references to\ntheir files, up to 64 work items keep sending callbacks to the one task\nwhich is running them. It never finds the list empty, never gets back to\nthe cancellation, the nodes stay, and so it goes on: a task with 60 pairs\nof rings which poll each other ran 280000 callbacks in 5 seconds, 20\nseconds after exit_group(). It ends when all the senders happen to be late\nat the same time. Until then the task keeps a CPU and the work items busy.\n\nAn exiting task can't be killed meanwhile. execve() cancels the requests in\nthe same way, so a live task can get stuck there as well, for minutes. If\nit takes more than five, the work items run into the\nWARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No\nprivilege is needed for any of this.\n\nIf the callback has met a task in cancellation, wait a little before it is\nsent again. Nobody has to wake the work item up for that: either the node\nis gone by then, or it is the turn of the next round."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "io_uring/io_uring.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "lessThan": "a22fb44e988b01b82235ea07f0bf0fc73e256596",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "lessThan": "2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "lessThan": "61c761fc21e00e45c33c2bb596be442d92fb8792",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "lessThan": "14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "lessThan": "abdc57c7ebabaaf0b622178a6a85834e1e54ff80",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "io_uring/io_uring.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "5.12",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "5.12",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.161",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.115",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.60",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.14",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {},
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/61c761fc21e00e45c33c2bb596be442d92fb8792",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a22fb44e988b01b82235ea07f0bf0fc73e256596",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/abdc57c7ebabaaf0b622178a6a85834e1e54ff80",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}