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Linux KernelOperating system · Linux

CVE-2021-47123

HIGH · 7.8 CVSS v3.1 Published 2024-03-15
Fix available
A fix is available. Upgrade to 5.12.10 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: io_uring: fix ltout double free on completion race Always remove linked timeout on io_link_timeout_fn() from the master request link list, otherwise we may get use-after-free when first io_link_timeout_fn() puts linked timeout in the fail path, and then will be found and put on master's free.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-415

The same block of memory is freed twice, corrupting the allocator's bookkeeping in ways an attacker can shape toward code execution. It usually stems from tangled ownership of a pointer. The fix is clear, single ownership of each allocation and clearing pointers once they are freed.

General guidance for the double free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 5.11, < 5.12.10= 5.13

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.12.10 or later
Fixed in 5.12.10
Vendor patch git.kernel.org →
Recommended fix High confidence

Kernel version 5.12.10, 5.13.1, or 5.14+ (any stable version beyond the affected range)

  1. 1. Identify the currently running kernel version using `uname -r` or `cat /proc/version`
  2. 2. Check if the running kernel version is affected: versions 5.11.x through 5.12.9, or exactly 5.13
  3. 3. Plan for a system reboot after kernel upgrade
  4. 4. Upgrade the Linux kernel to version 5.12.10 or later in the 5.12.x stable series, OR version 5.13.1 or later in the 5.13.x series, OR any version 5.14 and above
  5. 5. For package-based distributions (Debian, Ubuntu, RHEL, CentOS, etc.), use the distribution's package manager to install the latest available kernel (e.g., `apt-get update && apt-get upgrade` or `yum update`)
  6. 6. Ensure GRUB is updated to boot the new kernel (most distribution installers handle this automatically)
  7. 7. Reboot the system into the new kernel
  8. 8. Verify the new kernel version is running with `uname -r` and confirm it is 5.12.10+, 5.13.1+, or 5.14+
Caveat Kernel upgrades may require rebooting the system and could introduce compatibility changes with third-party kernel modules; ensure any proprietary drivers (NVIDIA, etc.) are compatible with the target kernel version

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-47123 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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