FKIE_CVE-2026-99231
Vulnerability from fkie_nvd - Published: 2026-11-02 16:17 - Updated: 2026-11-03 20:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
io_uring/waitid: own the request before clearing ->head
io_waitid_remove_wq() only takes the wait queue lock if ->head is set.
io_waitid_wait() clears ->head first thing, before it tries to become the
owner of the request by bumping ->refs. If somebody else owns the request
at that point, nothing keeps it from completing the request while the
wake up handler is still going to touch it:
CPU0 (io_waitid_wait) CPU1 (io_waitid, holds a ref)
list_del_init(&wait->entry)
smp_store_release(&iw->head, NULL)
__do_wait() finds another child
io_waitid_remove_wq()
// ->head == NULL, no locking
io_waitid_finish(), IOU_COMPLETE
// request freed and reused
atomic_fetch_inc(&iw->refs)
The same goes for __io_waitid_cancel() if it claims the request in that
window. ->refs is part of the per opcode data of the request, so this
increments whatever the next user of the request keeps there. If that
happens to be zero, the handler concludes that it owns the request, and
queues io_waitid_cb() for it. With the window held open by a delay, and
the request reused for a receive that is waiting for data:
BUG: KASAN: slab-use-after-free in __wake_up_common+0x1ca/0x1f0
__wake_up_sync_key+0x36/0x50
sock_def_readable+0xf1/0x420
unix_stream_sendmsg+0x60b/0x1110
Allocated by task 87:
io_arm_apoll+0x1ed/0x940
Freed by task 87:
__io_submit_flush_completions+0x118d/0x1a10
tctx_task_work_run+0x327/0x950
Only clear ->head once the handler owns the request. If it doesn't, the
owner finds ->head set and has to wait for the lock, which is held by the
caller of the handler. Deleting the already deleted entry again is
harmless.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"io_uring/waitid.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "bf01da1a9cca4a54e5c30b8344e52c26afb87be7",
"status": "affected",
"version": "09951a4d37e33b0197afc7fb77e39f09a3213ee6",
"versionType": "git"
},
{
"lessThan": "8381a912c65b8de16e8a848225c7c5a56b6ea834",
"status": "affected",
"version": "934ffdd1cdef232eb125e63c2ebafb7f2deff6af",
"versionType": "git"
},
{
"lessThan": "c10ad2813e15186fb51b37a4d17fafddc99e89a5",
"status": "affected",
"version": "ab673c1bcaf20ac70352eeb6bf5b828462676693",
"versionType": "git"
},
{
"lessThan": "c254eec4364b9f4b4cbdce43be3fb4df5a651a70",
"status": "affected",
"version": "ab673c1bcaf20ac70352eeb6bf5b828462676693",
"versionType": "git"
},
{
"lessThan": "6.12.115",
"status": "affected",
"version": "6.12.113",
"versionType": "semver"
},
{
"lessThan": "6.18.60",
"status": "affected",
"version": "6.18.52",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"io_uring/waitid.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.19"
},
{
"lessThan": "6.19",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.115",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.60",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.14",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.4-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/waitid: own the request before clearing -\u003ehead\n\nio_waitid_remove_wq() only takes the wait queue lock if -\u003ehead is set.\nio_waitid_wait() clears -\u003ehead first thing, before it tries to become the\nowner of the request by bumping -\u003erefs. If somebody else owns the request\nat that point, nothing keeps it from completing the request while the\nwake up handler is still going to touch it:\n\nCPU0 (io_waitid_wait) CPU1 (io_waitid, holds a ref)\nlist_del_init(\u0026wait-\u003eentry)\nsmp_store_release(\u0026iw-\u003ehead, NULL)\n __do_wait() finds another child\n io_waitid_remove_wq()\n // -\u003ehead == NULL, no locking\n io_waitid_finish(), IOU_COMPLETE\n // request freed and reused\natomic_fetch_inc(\u0026iw-\u003erefs)\n\nThe same goes for __io_waitid_cancel() if it claims the request in that\nwindow. -\u003erefs is part of the per opcode data of the request, so this\nincrements whatever the next user of the request keeps there. If that\nhappens to be zero, the handler concludes that it owns the request, and\nqueues io_waitid_cb() for it. With the window held open by a delay, and\nthe request reused for a receive that is waiting for data:\n\n BUG: KASAN: slab-use-after-free in __wake_up_common+0x1ca/0x1f0\n __wake_up_sync_key+0x36/0x50\n sock_def_readable+0xf1/0x420\n unix_stream_sendmsg+0x60b/0x1110\n Allocated by task 87:\n io_arm_apoll+0x1ed/0x940\n Freed by task 87:\n __io_submit_flush_completions+0x118d/0x1a10\n tctx_task_work_run+0x327/0x950\n\nOnly clear -\u003ehead once the handler owns the request. If it doesn\u0027t, the\nowner finds -\u003ehead set and has to wait for the lock, which is held by the\ncaller of the handler. Deleting the already deleted entry again is\nharmless."
}
],
"id": "CVE-2026-99231",
"lastModified": "2026-11-03T20:18:28.990",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-11-02T16:17:48.060",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/8381a912c65b8de16e8a848225c7c5a56b6ea834"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/bf01da1a9cca4a54e5c30b8344e52c26afb87be7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/c10ad2813e15186fb51b37a4d17fafddc99e89a5"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/c254eec4364b9f4b4cbdce43be3fb4df5a651a70"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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