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Linux KernelOperating system · Linux

CVE-2025-39718

MEDIUM · 5.5 CVSS v3.1 Published 2025-09-05
Fix available
A fix is available. Upgrade to 6.1.149 / 6.6.103 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: vsock/virtio: Validate length in packet header before skb_put() When receiving a vsock packet in the guest, only the virtqueue buffer size is validated prior to virtio_vsock_skb_rx_put(). Unfortunately, virtio_vsock_skb_rx_put() uses the length from the packet header as the length argument to skb_put(), potentially resulting in SKB overflow if the host has gone wonky. Validate the length as advertised by the packet header before calling virtio_vsock_skb_rx_put().

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:>= 6.1.63, < 6.1.149>= 6.3, < 6.6.103>= 6.7, < 6.12.44>= 6.13, < 6.16.4
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
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 6.1.149 / 6.6.103 / 6.12.44 or later
Fixed in 6.1.1496.6.1036.12.44
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 6.1.149+, 6.6.103+, 6.12.44+, or 6.16.4+ (depending on your current branch)

  1. 1. Identify the current kernel version by running: uname -r
  2. 2. For Debian 11.0 (Bullseye) systems: Check if a patched kernel is available via security updates or backports using: apt update && apt-cache policy linux-image-$(uname -r)
  3. 3. If no patched kernel is available in Debian 11.0, apply the vendor patch from https://git.kernel.org/stable/c/0dab92484474587b82e8e0455839eaf5ac7bf894 by rebuilding the kernel package
  4. 4. For other Linux distributions: Upgrade to a fixed kernel version: 6.1.149 or later for the 6.1 branch, 6.6.103 or later for the 6.6 branch, 6.12.44 or later for the 6.12 branch, or 6.16.4 or later for the 6.13+ branches
  5. 5. After upgrading the kernel, reboot the system to load the fixed version
  6. 6. Verify the fix is applied by checking the kernel version: uname -r and confirming it is one of the fixed versions listed above
Caveat Kernel upgrades may require rebooting and could have compatibility implications with proprietary kernel modules or specific driver configurations

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 $2,850. 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-2025-39718 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
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