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Linux KernelOperating system · Linux

CVE-2021-40490

HIGH · 7.0 CVSS v3.1 Published 2021-09-03
Fix available
A fix is available. Upgrade to 4.4.284 / 4.9.283 or later.
See remediation →
72/100
Remediation priority · Elevated
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
A race condition was discovered in ext4_write_inline_data_end in fs/ext4/inline.c in the ext4 subsystem in the Linux kernel through 5.13.13.

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-362

Two operations that should be atomic can interleave, so an attacker who wins a narrow timing window reaches an inconsistent, exploitable state. These bugs are subtle and easy to miss in review. Fixing them properly means correct locking or atomic operations around the shared resource.

General guidance for the race condition 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:>= 3.8, < 4.4.284>= 4.5, < 4.9.283>= 4.10, < 4.14.247>= 4.15, < 4.19.207>= 4.20, < 5.4.145>= 5.5, < 5.10.63>= 5.11, < 5.13.15>= 5.14, < 5.14.2
FedoraOperating system
Affected:= 33= 34
Debian LinuxOperating system
Affected:= 9.0= 11.0
Solidfire Baseboard Management ControllerApplication
Affected:all versions
Aff A250 FirmwareOperating system
Affected:all versions
Fas 500f FirmwareOperating system
Affected:all versions
H300s FirmwareOperating system
Affected:all versions
H500s FirmwareOperating system
Affected:all versions

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
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/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 4.4.284 / 4.9.283 / 4.14.247 or later
Fixed in 4.4.2844.9.2834.14.247
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 5.14 or later; or distribution-specific kernel updates that include the ext4 fix (commit 9e445093e523f3277081314c864f708fd4bd34aa)

  1. 1. Identify the current kernel version using 'uname -r' or 'cat /proc/version'
  2. 2. For Linux systems: Upgrade the kernel to version 5.14 or later, which contains the fix for the ext4_write_inline_data_end race condition (commit 9e445093e523f3277081314c864f708fd4bd34aa)
  3. 3. For Fedora 33/34 systems: Run 'sudo dnf update kernel' to install the patched kernel
  4. 4. For Debian 9/11 systems: Run 'sudo apt-get update && sudo apt-get install linux-image' to get the patched kernel
  5. 5. After kernel upgrade, reboot the system to load the fixed kernel
  6. 6. For embedded firmware products (Aff A250, Fas 500f, H300s, H500s, H700s): Contact the vendor for firmware updates that address this vulnerability
Caveat Kernel upgrades may require rebooting services and could have compatibility implications with custom kernel modules or older system utilities

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-2021-40490 in production — separate from our analysis above.

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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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