CVE-2025-37906 (GCVE-0-2025-37906)

Vulnerability from cvelistv5 – Published: 2025-05-20 15:21 – Updated: 2026-08-05 11:58
VLAI
Title
ublk: fix race between io_uring_cmd_complete_in_task and ublk_cancel_cmd
Summary
In the Linux kernel, the following vulnerability has been resolved: ublk: fix race between io_uring_cmd_complete_in_task and ublk_cancel_cmd ublk_cancel_cmd() calls io_uring_cmd_done() to complete uring_cmd, but we may have scheduled task work via io_uring_cmd_complete_in_task() for dispatching request, then kernel crash can be triggered. Fix it by not trying to canceling the command if ublk block request is started.
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
Linux Linux Affected: 216c8f5ef0f209a3797292c487bdaa6991ab4b92 , < fb2eb9ddf556f93fef45201e1f9d2b8674bcc975 (git)
Affected: 216c8f5ef0f209a3797292c487bdaa6991ab4b92 , < f40139fde5278d81af3227444fd6e76a76b9506d (git)
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Linux Linux Affected: 6.7
Unaffected: 0 , < 6.7 (semver)
Unaffected: 6.14.6 , ≤ 6.14.* (semver)
Unaffected: 6.15 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/ublk_drv.c"
          ],
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          "vendor": "Linux",
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              "status": "affected",
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              "versionType": "git"
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              "status": "unaffected",
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              "versionType": "semver"
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            {
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nublk: fix race between io_uring_cmd_complete_in_task and ublk_cancel_cmd\n\nublk_cancel_cmd() calls io_uring_cmd_done() to complete uring_cmd, but\nwe may have scheduled task work via io_uring_cmd_complete_in_task() for\ndispatching request, then kernel crash can be triggered.\n\nFix it by not trying to canceling the command if ublk block request is\nstarted."
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              "value": "AV:L - The race is reached only through local interfaces \u2014 `/dev/ublk-control` and `/dev/ublkc*` io_uring passthrough commands plus block I/O to `/dev/ublkb*`. There is no remote or adjacent-network path into ublk_drv.\nAC:L - The attacker owns both sides of the race: one thread submits I/O to the ublk block device (queueing `ublk_cmd_tw_cb` task work) while another tears down the io_uring ring or issues `UBLK_CMD_STOP_DEV`, driving `ublk_cancel_cmd()`. The window can be hit repeatedly in a loop with high queue depth until it lands.\nPR:L - ublk explicitly supports `UBLK_F_UNPRIVILEGED_DEV`, where `ublk_ctrl_add_dev()` accepts non-`CAP_SYS_ADMIN` callers and all later control commands gate only on file permissions of `/dev/ublkc*`, so an ordinary local user (including inside a container) can create and drive the device. Only basic local-user access is needed, not real root.\nUI:N - The attacking process performs every step itself \u2014 creating the ublk device, issuing I/O, and triggering cancellation. No victim action or interaction is required.\nS:U - The corruption is confined to kernel heap objects (`io_kiocb`) within the same security authority; the ublk driver and io_uring both run in the kernel\u0027s own scope. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed io_uring request is dereferenced and re-completed, so an attacker who reclaims the slab object controls its contents and can have kernel data posted back through the CQE and the ublk io path. Per UAF guidance this constitutes a path to arbitrary kernel memory disclosure.\nI:H - The second `io_uring_cmd_done()` writes result fields into and relinks a freed `io_kiocb`, and the request is freed twice \u2014 a write-after-free plus double-free on a well-known io_uring slab that is a standard heap-spray target for control-flow hijack. This is high-integrity memory corruption, not a bounded write.\nA:H - The commit states plainly that \"kernel crash can be triggered,\" and the double completion corrupts io_uring\u0027s completion/task-work lists. Any unprivileged local user with a ublk device can panic the machine on demand."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-08-05T11:58:13.306Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/f40139fde5278d81af3227444fd6e76a76b9506d"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-37906",
    "datePublished": "2025-05-20T15:21:39.633Z",
    "dateReserved": "2025-04-16T04:51:23.966Z",
    "dateUpdated": "2026-08-05T11:58:13.306Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-08-11",
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      "percentile": "0.02232"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-30T09:29:18+00:00",
      "cve": "CVE-2025-37906",
      "id": "CVE-2025-37906",
      "initial_release_date": "2025-05-20T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel: ublk race condition causes kernel crash",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37906.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-07-31T01:14:56Z",
      "cve": "CVE-2025-37906",
      "id": "CVE-2025-37906",
      "initial_release_date": "2025-05-21T00:47:18Z",
      "product_status:known_not_affected": "455",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-37906",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-37906.json",
      "version": "12"
    }
  }
}



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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.

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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.


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