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CVE Record

CVE-2021-47040: io_uring: fix overflows checks in provide buffers

In the Linux kernel, the following vulnerability has been resolved: io_uring: fix overflows checks in provide buffers Colin reported before possible overflow and sign extension problems in io_provide_buffers_prep(). As Linus pointed out previous attempt did nothing useful, see d81269fecb8ce ("io_uring: fix provide_buffers sign extension"). Do that with help of check_<op>_overflow helpers. And fix struct io_provide_buf::len type, as it doesn't make much sense to keep it signed.

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 involving integer overflow and sign-extension checks while preparing provided buffers. The source bundle does not state a business impact, severity score, or known exploitation. Treat it as a kernel maintenance risk that matters most on systems running affected Linux kernels, especially shared hosts.

Executive priority

Moderate operational priority until vendor impact is confirmed. There is no evidence here of active exploitation or critical severity, but kernel vulnerabilities can affect shared infrastructure. Prioritize verification and routine kernel patching rather than emergency action based on this bundle alone.

Technical view

The resolved issue is in io_provide_buffers_prep(), where previous overflow and sign-extension handling was insufficient. The fix uses check_<op>_overflow helpers and changes io_provide_buf::len away from a signed type. The provided data lists Linux kernel versions as affected and points to stable kernel commits.

Likely exposure

Likely exposure is Linux systems running the affected kernel versions or downstream kernels that include the vulnerable io_uring code. Distribution backports may change status, so raw upstream version checks are not enough. Shared systems with untrusted local workloads deserve higher review priority.

Exploitation context

The source bundle marks KEV as false and provides no cited evidence of active exploitation. It also does not state exploit availability, required privileges, or concrete impact. The safest conclusion is that exploitation status and practical impact are not established by the provided evidence.

Researcher notes

Evidence is limited to the CVE description and kernel stable commit references. The bundle identifies the bug class but not impact, exploit path, privilege requirements, or CVSS. Researchers should validate against exact kernel source or vendor patches without inferring more than the sources state.

Mitigation direction

  • Map deployed kernel packages to vendor advisories for CVE-2021-47040.
  • Apply Linux kernel updates containing the cited stable io_uring fixes.
  • Prioritize shared hosts and systems running untrusted local workloads.
  • Use vendor guidance if patching is delayed; do not assume a configuration workaround.

Validation and detection

  • Inventory Linux kernel versions across servers, containers hosts, and appliances.
  • Confirm whether vendor kernels include the referenced stable fixes or equivalent backports.
  • Check vulnerability scanner findings against distribution-specific kernel advisory status.
  • Record unresolved systems with business owner, patch plan, and exception date.
Prepared
Confidence
medium
Sources
6

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-2021-47040 mapping review

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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
5Source 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
LinuxLinuxefe68c1ca8f49e8c06afd74b699411bfbb8ba1ff, efe68c1ca8f49e8c06afd74b699411bfbb8ba1ff, efe68c1ca8f49e8c06afd74b699411bfbb8ba1ff, efe68c1ca8f49e8c06afd74b699411bfbb8ba1ffunaffected
LinuxLinux5.8, 0, 5.10.37, 5.11.21, 5.12.4, 5.13affected
Weakness

CWE details

No CWE listed

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