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Linux KernelOperating system · Linux

CVE-2025-38709

MEDIUM · 5.5 CVSS v3.1 Published 2025-09-04
Fix available
A fix is available. Upgrade to 6.6.109 / 6.12.43 or later.
See remediation →
57/100
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
In the Linux kernel, the following vulnerability has been resolved: loop: Avoid updating block size under exclusive owner Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size. Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it.

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

A detailed technical summary for this CVE is being prepared.

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:< 6.6.109>= 6.7, < 6.12.43>= 6.13, < 6.15.11>= 6.16, < 6.16.2

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 6.6.109 / 6.12.43 / 6.15.11 or later
Fixed in 6.6.1096.12.436.15.11
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to kernel version 6.6.109, 6.12.43, 6.15.11, or 6.16.2 (or later stable release in the respective branch)

  1. Identify the currently running kernel version using `uname -r`
  2. Check if the installed kernel version is one of the affected versions: < 6.6.109, >= 6.7 and < 6.12.43, >= 6.13 and < 6.15.11, or >= 6.16 and < 6.16.2
  3. If affected, update the kernel package to a fixed version: 6.6.109 or later for the 6.6.y branch, 6.12.43 or later for the 6.12.y branch, 6.15.11 or later for the 6.15.y branch, or 6.16.2 or later for the 6.16.y branch
  4. Reboot the system to load the fixed kernel
  5. Verify the fix is applied by checking the kernel version and confirming the loop module has the patch (or by reviewing the commit at git.kernel.org/stable/c/139a000d20f2f38ce34296feddd641d730fe1c08)
Caveat Kernel upgrades may require matching kernel modules; ensure dependent modules are compatible. Some older drivers or proprietary modules may not work with newer kernels.

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 $1,600. 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-2025-38709 in production — separate from our analysis above.

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What this is

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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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