{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-40047",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-40047"
  ],
  "published": "2025-10-28T11:50:45Z",
  "summary": "io_uring/waitid: always prune wait queue entry in io_waitid_wait()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/waitid: always prune wait queue entry in io_waitid_wait()\n\nFor a successful return, always remove our entry from the wait queue\nentry list. Previously this was skipped if a cancelation was in\nprogress, but this can race with another invocation of the wait queue\nentry callback.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-40047"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/696ba6032081e617564a8113a001b8d7943cb928"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3e2205db2f0608898d535da1964e1b376aacfdaa"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2f8229d53d984c6a05b71ac9e9583d4354e3b91f"
    }
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  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerability is reached through the io_uring syscall interface (`io_uring_setup`/`io_uring_enter` submitting an `IORING_OP_WAITID` SQE) plus process-management signals, all of which require local access to the system. Per kernel scoring guidance, io_uring bugs are Local.\nAC:L - The attacker controls both sides of the race: it drives the wait-queue wakeups at arbitrary rate by forking children and looping SIGSTOP/SIGCONT (`do_notify_parent_cldstop` \u2192 `__wake_up_parent`), while concurrently submitting `IORING_OP_ASYNC_CANCEL` or tearing down the ring from another thread to grab the competing reference. syzbot produced a working reproducer and confirmed the fix, showing the window is hit reliably.\nPR:L - Any unprivileged local user can create an io_uring ring \u2014 `sysctl_io_uring_disabled` defaults to 0 and `IORING_OP_WAITID` carries no capability check \u2014 and waiting on one's own forked children needs no privilege at all. No capabilities, user namespaces, or root are required.\nUI:N - The attacker's own process performs every step: submitting the waitid SQE, forking and signalling the children that generate wakeups, and issuing the concurrent cancel. No action by any other user is needed.\nS:U - The use-after-free corrupts kernel heap memory and control flow within the same kernel security authority, yielding standard local privilege escalation. No VM, IOMMU, or other security-boundary crossing is involved.\nC:H - This is a use-after-free on a `struct io_waitid_async` allocated from a general-purpose kmalloc slab, which the attacker can reclaim and shape via heap spraying. The stale wait-queue entry is then dereferenced by `__wake_up_common()` and `list_del_init()`, giving a read primitive over reclaimed kernel memory that can be leveraged for arbitrary kernel memory disclosure.\nI:H - `list_del_init()` on the freed entry performs `prev->next = next; next->prev = prev` using pointers read from attacker-reclaimed memory, yielding a controlled write of a controlled pointer to a controlled address. Additionally `__wake_up_common()` calls `curr->func(...)` on the freed entry, providing a direct indirect-call/control-flow hijack primitive leading to kernel code execution.\nA:H - Even without weaponization, the dangling wait-queue entry and the list-corrupting `list_del_init()` on freed memory produce KASAN splats, list debug BUGs, and kernel oopses/panics \u2014 this is exactly how syzbot detected it. The race can be re-triggered in a tight loop, so an unprivileged user can crash the machine at will."
    }
  }
}