io_uring/waitid: own the request before clearing ->head

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-99231
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-02 16:17:48 UTC
Updated2026-11-06 18:18:33 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001150000 probability, percentile 0.015780000 (date 2026-11-03)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 09951a4d37e33b0197afc7fb77e39f09a3213ee6 bf01da1a9cca4a54e5c30b8344e52c26afb87be7 git Not specified
CNA Linux Linux affected 934ffdd1cdef232eb125e63c2ebafb7f2deff6af 8381a912c65b8de16e8a848225c7c5a56b6ea834 git Not specified
CNA Linux Linux affected ab673c1bcaf20ac70352eeb6bf5b828462676693 c10ad2813e15186fb51b37a4d17fafddc99e89a5 git Not specified
CNA Linux Linux affected ab673c1bcaf20ac70352eeb6bf5b828462676693 6e11ce129b34fb9a43b2bbe838df49ea52878d5c git Not specified
CNA Linux Linux affected ab673c1bcaf20ac70352eeb6bf5b828462676693 c254eec4364b9f4b4cbdce43be3fb4df5a651a70 git Not specified
CNA Linux Linux affected 6.12.113 6.12.115 semver Not specified
CNA Linux Linux affected 6.18.52 6.18.60 semver Not specified
CNA Linux Linux affected 6.19 Not specified
CNA Linux Linux unaffected 6.19 semver Not specified
CNA Linux Linux unaffected 6.12.115 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.60 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.14 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3.2 7.3.* semver Not specified
CNA Linux Linux unaffected 7.4-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/c254eec4364b9f4b4cbdce43be3fb4df5a651a70 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c10ad2813e15186fb51b37a4d17fafddc99e89a5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6e11ce129b34fb9a43b2bbe838df49ea52878d5c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bf01da1a9cca4a54e5c30b8344e52c26afb87be7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8381a912c65b8de16e8a848225c7c5a56b6ea834 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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