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CVE Record

CVE-2021-47569: io_uring: fail cancellation for EXITING tasks

In the Linux kernel, the following vulnerability has been resolved: io_uring: fail cancellation for EXITING tasks WARNING: CPU: 1 PID: 20 at fs/io_uring.c:6269 io_try_cancel_userdata+0x3c5/0x640 fs/io_uring.c:6269 CPU: 1 PID: 20 Comm: kworker/1:0 Not tainted 5.16.0-rc1-syzkaller #0 Workqueue: events io_fallback_req_func RIP: 0010:io_try_cancel_userdata+0x3c5/0x640 fs/io_uring.c:6269 Call Trace: <TASK> io_req_task_link_timeout+0x6b/0x1e0 fs/io_uring.c:6886 io_fallback_req_func+0xf9/0x1ae fs/io_uring.c:1334 process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298 worker_thread+0x658/0x11f0 kernel/workqueue.c:2445 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> We need original task's context to do cancellations, so if it's dying and the callback is executed in a fallback mode, fail the cancellation attempt.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel io_uring bug in task cancellation handling. The public record shows a kernel warning when cancellation is attempted after the original task is exiting. The available sources do not describe remote compromise, privilege escalation, or confirmed exploitation.

Executive priority

Treat this as a patch-management item, not an emergency, unless vendor advisories add higher impact details. Prioritize confirmation on Linux 5.15/5.16-era fleets and shared hosting or multi-tenant systems.

Technical view

The flaw is in io_uring cancellation logic. Cancellations require the original task context; when the task is EXITING and work runs through fallback handling, the kernel should fail the cancellation attempt. Stable commits correct that behavior. Public metadata lists affected Linux 5.15/5.16-era versions, but downstream backports require vendor confirmation.

Likely exposure

Exposure is limited to Linux systems running affected kernel builds with io_uring support. The source data identifies Linux 5.15/5.16-era affected versions, but exact exposure depends on distribution backports and vendor kernel packaging.

Exploitation context

No active exploitation is supported by the provided sources, and KEV is false. The bundle shows a syzkaller-style kernel warning trace and a fix, but does not document exploitability, attacker prerequisites, or real-world abuse.

Researcher notes

The public record is sparse: no CVSS, CWE, or detailed impact statement is provided. Analysis should stay close to the kernel commit rationale: failing cancellation for EXITING tasks prevents invalid cancellation attempts when original task context is unavailable.

Mitigation direction

  • Apply vendor-supported kernel updates containing the referenced stable fixes.
  • Check distribution advisories for backported fix status before relying on upstream version numbers.
  • Prioritize systems on Linux 5.15/5.16-era kernels until vendor status is confirmed.
  • If no patch is available, follow vendor guidance for temporary risk reduction.

Validation and detection

  • Inventory kernel versions and distribution build identifiers across Linux hosts.
  • Map each build to vendor advisories or the referenced stable commits.
  • Review kernel changelogs for the io_uring cancellation fix.
  • Confirm patched systems rebooted into the updated kernel.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47569 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux89b263f6d56e683ddcf7643140271ef6e36c72b9, 89b263f6d56e683ddcf7643140271ef6e36c72b9unaffected
LinuxLinux5.15, 0, 5.15.6, 5.16affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.