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NVD / CVE Program· CNA Linux

CVE-2026-99231: io_uring/waitid: own the request before clearing ->head

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.11% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 6.12.115, 6.18.60, 8381a912c65b8de16e8a848225c7c5a56b6ea834.

Low priority for now. Upgrade to Linux Linux 6.12.115, 6.18.60, 8381a912c65b8de16e8a848225c7c5a56b6ea834 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Nov 2, 2026
Updated
Nov 3, 2026
EPSS
0.1% · 1th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 6.19affected
    • 09951a4d37e33b0197afc7fb77e39f09a3213ee6 and later · before bf01da1a9cca4a54e5c30b8344e52c26afb87be7affected · git
    • 934ffdd1cdef232eb125e63c2ebafb7f2deff6af and later · before 8381a912c65b8de16e8a848225c7c5a56b6ea834affected · git
    • ab673c1bcaf20ac70352eeb6bf5b828462676693 and later · before c10ad2813e15186fb51b37a4d17fafddc99e89a5affected · git
    • ab673c1bcaf20ac70352eeb6bf5b828462676693 and later · before c254eec4364b9f4b4cbdce43be3fb4df5a651a70affected · git
    • 6.12.113 and later · before 6.12.115affected · semver
    • 6.18.52 and later · before 6.18.60affected · semver
    • before 6.19not affected · semver
    • 6.12.115 and later · up to and including 6.12.*not affected · semver
    • 6.18.60 and later · up to and including 6.18.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:13linuxbefore 6.12.115-16.12.115-1
Debian:14linuxfrom 0—

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99229Nov 2, 2026 · io_uring/wait: don't spin on a stuck overflow list
    0Monitor
  • ← EarlierCVE-2026-99230Nov 2, 2026 · io_uring/cmd: don't leave list poison in ->hash_node
    0Monitor
  • Later →CVE-2026-99232Nov 2, 2026 · tracing/syscalls: Use copy_from_user for the faultable syscall buffer
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux6.12.115Vendor (CNA)
Linux Linux6.18.60Vendor (CNA)
Linux Linux8381a912c65b8de16e8a848225c7c5a56b6ea834Vendor (CNA)
Linux Linuxbf01da1a9cca4a54e5c30b8344e52c26afb87be7Vendor (CNA)
Linux Linuxc10ad2813e15186fb51b37a4d17fafddc99e89a5Vendor (CNA)
Linux Linuxc254eec4364b9f4b4cbdce43be3fb4df5a651a70Vendor (CNA)
debian:linux6.12.115-1 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 5, 2026+2 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓
  2. Exploit maturity— → none

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records