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Linux KernelOperating system · Linux

CVE-2025-39848

MEDIUM · 5.5 CVSS v3.1 Published 2025-09-19
Fix available
A fix is available. Upgrade to 5.4.299 / 5.10.243 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: ax25: properly unshare skbs in ax25_kiss_rcv() Bernard Pidoux reported a regression apparently caused by commit c353e8983e0d ("net: introduce per netns packet chains"). skb->dev becomes NULL and we crash in __netif_receive_skb_core(). Before above commit, different kind of bugs or corruptions could happen without a major crash. But the root cause is that ax25_kiss_rcv() can queue/mangle input skb without checking if this skb is shared or not. Many thanks to Bernard Pidoux for his help, diagnosis and tests. We had a similar issue years ago fixed with commit 7aaed57c5c28 ("phonet: properly unshare skbs in phonet_rcv()").

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-401

Allocated memory is never released on some path, so a long-running service or a repeatedly triggered request steadily consumes memory until performance degrades or the process crashes. Attackers exploit it by simply driving the leaking path. Remediation is pairing every allocation with a release and using ownership patterns or tooling to catch what leaks.

General guidance for the memory leak 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:>= 2.6.12.1, < 5.4.299>= 5.5, < 5.10.243>= 5.11, < 5.15.192>= 5.16, < 6.1.151>= 6.2, < 6.6.105>= 6.7, < 6.12.46>= 6.13, < 6.16.6= 2.6.12= 6.17
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 5.4.299 / 5.10.243 / 5.15.192 or later
Fixed in 5.4.2995.10.2435.15.192
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 5.4.299+, 5.10.243+, 5.15.192+, or 6.1.151+ (or Debian 11.0 vendor updates)

  1. Identify the currently running Linux kernel version using `uname -r`
  2. Determine which version branch your kernel belongs to (e.g., 5.4.x, 5.10.x, 5.15.x, 6.1.x)
  3. Upgrade the kernel to a version >= 5.4.299 (for 5.4.x branches), >= 5.10.243 (for 5.10.x branches), >= 5.15.192 (for 5.15.x branches), or >= 6.1.151 (for 6.1.x and later branches
  4. On Debian 11.0 systems, apply vendor updates: run `apt update && apt upgrade linux-image-*` to receive the patched kernel
  5. Reboot the system to load the updated kernel
  6. Verify the fix by checking the kernel version after reboot with `uname -r`
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with custom kernel modules; ensure dependent modules are rebuilt for the new 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 $1,600. 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-2025-39848 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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