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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-99255: io_uring/io-wq: don't hide a link from cancellations

Noroxi assessment

Priority: Monitor (action score 0/100)

  • 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: 0.19% (FIRST EPSS).
  • Fixed version: Linux Linux 3e02b8df0e9fa1423ac2a4e03409a9329c30ac49, 436d48a2ed13112d2d27085325838e5bce6b4507, 92e20e9c72bdf6cfa6f84eded7b33399bc7061da.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 3e02b8df0e9fa1423ac2a4e03409a9329c30ac49, 436d48a2ed13112d2d27085325838e5bce6b4507, 92e20e9c72bdf6cfa6f84eded7b33399bc7061da 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/io-wq: don't hide a link from cancellations A task that exits cancels its tracked requests and waits until they are gone. io_uring_cancel_generic() looks everywhere a request can be, and goes to sleep if it found nothing to cancel. It is woken up each time one of the requests of the task is completed by task work or freed. When io-wq is done with a request that has a link, there is a time in which the next request of the link can't be found: io_worker_handle_work() io_assign_current_work(worker, NULL) io_wq_free_work(work) io_req_find_next() // takes the link off the request io_free_req() // task work for the task io_assign_current_work(worker, linked) io_run_task_work() cond_resched() worker->cur_work = linked It is not pending, it is not the current work of a worker, and it is not yet on the list that it is about to be parked on. If the pass that the exiting task makes because of io_free_req() falls into that time, it finds nothing and the task goes to sleep. The worker then runs the link, which IO_WQ_BIT_EXIT doesn't prevent for bounded work. If that parks the request nothing is completed or freed, and nobody wakes up the task. If it is the process that exits it can't be killed any more either. NOP, IOSQE_ASYNC | IOSQE_IO_LINK FUTEX_WAIT, FUTEX2_PRIVATE exit of the thread, or of the process, up to 63us later With four of these per round 5 to 8 of 10,000 rounds hang (4 CPUs, KVM): io_uring_cancel_generic do_exit Commit f8b632e89a10 ("io_uring: tighten task exit cancellations") is about the same gap, and makes the task look again for whatever happens before io_free_req(). Free the request once the link is the current work of the worker, or pending. Whoever is woken up by that can find the link, until it is parked where cancellations look as well. To do so split io_wq_free_work() in two.

—No exploit Fix available
Published
Nov 3, 2026
Updated
Nov 3, 2026
EPSS
0.1% · 9th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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Noroxi analysis

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Affected systems

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—

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

    • 5.5affected
    • 768134d4f48109b90f4248feecbeeb7d684e410c and later · before 98470f164286f7f62aaee519d4d11b9370ce6d7baffected · git
    • 768134d4f48109b90f4248feecbeeb7d684e410c and later · before d39ebc7a583d650b1d6da9b45e2ce96ad4d877e4affected · git
    • 768134d4f48109b90f4248feecbeeb7d684e410c and later · before ebe8e97fb99d9f374c482902a00677cfd24a6c27affected · git
    • 768134d4f48109b90f4248feecbeeb7d684e410c and later · before 3e02b8df0e9fa1423ac2a4e03409a9329c30ac49affected · git
    • 768134d4f48109b90f4248feecbeeb7d684e410c and later · before 92e20e9c72bdf6cfa6f84eded7b33399bc7061daaffected · git
    • 768134d4f48109b90f4248feecbeeb7d684e410c and later · before 436d48a2ed13112d2d27085325838e5bce6b4507affected · git
    • before 5.5not affected · semver
    • 6.1.191 and later · up to and including 6.1.*not affected · semver
    • 6.6.161 and later · up to and including 6.6.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-16.12.115-1

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-2026-99253Nov 3, 2026 · io_uring/cancel: rearm local work wake up before sleep
    0Monitor
  • ← EarlierCVE-2026-99254Nov 3, 2026 · io_uring: don't flood a cancelling task with task_work
    0Monitor
  • Later →CVE-2026-99256Nov 3, 2026 · dm cache: fix issue with background work locking
    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 Linux3e02b8df0e9fa1423ac2a4e03409a9329c30ac49Vendor (CNA)
Linux Linux436d48a2ed13112d2d27085325838e5bce6b4507Vendor (CNA)
Linux Linux92e20e9c72bdf6cfa6f84eded7b33399bc7061daVendor (CNA)
Linux Linux98470f164286f7f62aaee519d4d11b9370ce6d7bVendor (CNA)
Linux Linuxd39ebc7a583d650b1d6da9b45e2ce96ad4d877e4Vendor (CNA)
Linux Linuxebe8e97fb99d9f374c482902a00677cfd24a6c27Vendor (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

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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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

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

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References

Show all references (5 more)

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

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