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Linux KernelOperating system · Linux

CVE-2025-38685

HIGH · 7.8 CVSS v3.1 Published 2025-09-04
Fix available
A fix is available. Upgrade to 5.15.190 / 6.1.149 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: fbdev: Fix vmalloc out-of-bounds write in fast_imageblit This issue triggers when a userspace program does an ioctl FBIOPUT_CON2FBMAP by passing console number and frame buffer number. Ideally this maps console to frame buffer and updates the screen if console is visible. As part of mapping it has to do resize of console according to frame buffer info. if this resize fails and returns from vc_do_resize() and continues further. At this point console and new frame buffer are mapped and sets display vars. Despite failure still it continue to proceed updating the screen at later stages where vc_data is related to previous frame buffer and frame buffer info and display vars are mapped to new frame buffer and eventully leading to out-of-bounds write in fast_imageblit(). This bheviour is excepted only when fg_console is equal to requested console which is a visible console and updates screen with invalid struct references in fbcon_putcs().

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-787

The program writes past the bounds of a buffer, overwriting adjacent memory an attacker can turn to their advantage. Crafted input can overwrite control data and redirect execution. Remediation is validating every index and length before a write, plus modern memory-safety mitigations.

General guidance for the out-of-bounds write 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:>= 2.6.13, < 5.15.190>= 5.16, < 6.1.149>= 6.2, < 6.6.103>= 6.7, < 6.12.43>= 6.13, < 6.15.11>= 6.16, < 6.16.2= 2.6.12
Debian LinuxOperating system
Affected:= 11.0

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 5.15.190 / 6.1.149 / 6.6.103 or later
Fixed in 5.15.1906.1.1496.6.103
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 5.15.190 / 6.1.149 / 6.6.103 / 6.12.43 or later (depending on which branch you are on)

  1. Identify the current kernel version using `uname -r`
  2. Determine which kernel branch is applicable (5.15.x, 6.1.x, 6.6.x, or 6.7+/6.12.x)
  3. For Debian 11 (bullseye), check if Debian has released a security update for this CVE using `apt-get update && apt-get upgrade` or check `dpkg -l | grep linux-image`
  4. If no Debian patch is available, upgrade the kernel to a fixed version: 5.15.190+, 6.1.149+, 6.6.103+, or 6.12.43+
  5. After kernel upgrade, reboot the system to load the fixed kernel
  6. Verify the fix is applied by checking `uname -r` shows a version >= the fixed version for your branch
Caveat Kernel upgrades may require rebooting the system and could introduce compatibility issues with custom kernel modules or specific hardware drivers; ensure backups and test in non-production environment first

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 $3,200. 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-2025-38685 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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