CVE-2026-46274 (GCVE-0-2026-46274)
Vulnerability from cvelistv5
Published
2026-06-08 14:30
Modified
2026-08-05 12:30
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: io-wq: check that the predecessor is hashed in io_wq_remove_pending() io_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled work was the tail of its hash bucket. When doing this, it checks whether the preceding entry in acct->work_list has the same hash value, but never checks that the predecessor is hashed at all. io_get_work_hash() is simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash bits are never set for non-hashed work, so it returns 0. Thus, when a hashed bucket-0 work is cancelled while a non-hashed work is its list predecessor, the check spuriously passes and a pointer to the non-hashed io_kiocb is stored in wq->hash_tail[0]. Because non-hashed work is dequeued via the fast path in io_get_next_work(), which never touches hash_tail[], the stale pointer is never cleared. Therefore, after the non-hashed io_kiocb completes and is freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The io_wq is per-task (tctx->io_wq) and survives ring open/close, so the dangling pointer persists for the lifetime of the task; the next hashed bucket-0 enqueue dereferences it in io_wq_insert_work() and wq_list_add_after() writes through freed memory. Add the missing io_wq_is_hashed() check so a non-hashed predecessor never inherits a hash_tail[] slot.
References
Impacted products
Vendor Product Version
Linux Linux Version: 204361a77f4018627addd4a06877448f088ddfc0
Version: 204361a77f4018627addd4a06877448f088ddfc0
Version: 204361a77f4018627addd4a06877448f088ddfc0
Version: 204361a77f4018627addd4a06877448f088ddfc0
Version: 204361a77f4018627addd4a06877448f088ddfc0
Version: 13f35a2c0fd5c6a4fcd8903542b053bcc914fcf5
Version: 5.8.6   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "io_uring/io-wq.c"
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "6.12.91",
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            },
            {
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              "status": "unaffected",
              "version": "6.18.33",
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            },
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              "status": "unaffected",
              "version": "7.0.10",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.141",
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                  "vulnerable": true
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio-wq: check that the predecessor is hashed in io_wq_remove_pending()\n\nio_wq_remove_pending() needs to fix up wq-\u003ehash_tail[] if the cancelled\nwork was the tail of its hash bucket. When doing this, it checks whether\nthe preceding entry in acct-\u003ework_list has the same hash value, but\nnever checks that the predecessor is hashed at all. io_get_work_hash()\nis simply atomic_read(\u0026work-\u003eflags) \u003e\u003e IO_WQ_HASH_SHIFT, and the hash\nbits are never set for non-hashed work, so it returns 0. Thus, when a\nhashed bucket-0 work is cancelled while a non-hashed work is its list\npredecessor, the check spuriously passes and a pointer to the non-hashed\nio_kiocb is stored in wq-\u003ehash_tail[0].\n\nBecause non-hashed work is dequeued via the fast path in\nio_get_next_work(), which never touches hash_tail[], the stale pointer\nis never cleared. Therefore, after the non-hashed io_kiocb completes and\nis freed back to req_cachep, wq-\u003ehash_tail[0] is a dangling pointer. The\nio_wq is per-task (tctx-\u003eio_wq) and survives ring open/close, so the\ndangling pointer persists for the lifetime of the task; the next hashed\nbucket-0 enqueue dereferences it in io_wq_insert_work() and\nwq_list_add_after() writes through freed memory.\n\nAdd the missing io_wq_is_hashed() check so a non-hashed predecessor\nnever inherits a hash_tail[] slot."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only through io_uring syscalls (io_uring_setup/io_uring_enter) that enqueue and cancel async io-wq work; there is no network, adjacent-radio, or physical-device entry path to io_wq_remove_pending().\nAC:L - An attacker fully controls the trigger sequence\u2014queue a non-hashed async request, queue a hashed bucket-0 request behind it, cancel the hashed pending work, let the non-hashed work complete, then enqueue another hashed bucket-0 request\u2014with no dependence on uncontrollable timing or rare kernel configuration.\nPR:L - Any unprivileged local user who can invoke io_uring (default when kernel.io_uring_disabled=0) can drive the cancel/enqueue sequence; no real-root or special capability beyond normal local process access is required.\nUI:N - Exploitation requires only the attacker\u0027s own io_uring submissions and cancellations; no victim user action such as opening files or mounting filesystems is needed beyond what the attacker initiates.\nS:U - The flaw corrupts kernel heap memory within the same kernel security domain to escalate from local user to kernel privileges; it does not inherently cross a VM/host or IOMMU boundary on its own.\nC:H - The stale hash_tail pointer is a use-after-free of a freed io_kiocb slab object; subsequent dereferences in io_wq_insert_work() read freed memory and UAF heap corruption is routinely weaponizable for arbitrary kernel memory disclosure.\nI:H - io_wq_insert_work() calls wq_list_add_after(), which writes attacker-influenced list pointers through the freed io_kiocb\u0027s list.next field, providing a controlled heap write primitive suitable for further memory corruption or code execution.\nA:H - Dereferencing and writing through the dangling hash_tail pointer can cause kernel oops/panic from invalid slab access, and successful heap corruption can crash or hang the system even before full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:30:57.842Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d6bda9df0c0a3080804181464d5c0f4d78a4e769"
        },
        {
          "url": "https://git.kernel.org/stable/c/5a20ebf0c81b61f5ea3b1b529c100cad69b9f603"
        },
        {
          "url": "https://git.kernel.org/stable/c/252c5051dba9c709b6a72f2866f93e5e618b3f06"
        },
        {
          "url": "https://git.kernel.org/stable/c/d376c131af7c7739a87ff037ed2fdb67c2542c8a"
        },
        {
          "url": "https://git.kernel.org/stable/c/d6a2d7b04b5a093021a7a0e2e69e9d5237dfa8cc"
        }
      ],
      "title": "io-wq: check that the predecessor is hashed in io_wq_remove_pending()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-46274",
    "datePublished": "2026-06-08T14:30:53.323Z",
    "dateReserved": "2026-05-13T15:03:33.109Z",
    "dateUpdated": "2026-08-05T12:30:57.842Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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