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Linux KernelOperating system · Linux

CVE-2025-39873

HIGH · 7.8 CVSS v3.1 Published 2025-09-23
Fix available
A fix is available. Upgrade to 5.15.194 / 6.1.153 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: can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB can_put_echo_skb() takes ownership of the SKB and it may be freed during or after the call. However, xilinx_can xcan_write_frame() keeps using SKB after the call. Fix that by only calling can_put_echo_skb() after the code is done touching the SKB. The tx_lock is held for the entire xcan_write_frame() execution and also on the can_get_echo_skb() side so the order of operations does not matter. An earlier fix commit 3d3c817c3a40 ("can: xilinx_can: Fix usage of skb memory") did not move the can_put_echo_skb() call far enough. [mkl: add "commit" in front of sha1 in patch description] [mkl: fix indention]

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-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free 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:>= 4.19, < 5.15.194>= 5.16, < 6.1.153>= 6.2, < 6.6.107>= 6.7, < 6.12.48>= 6.13, < 6.16.8= 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
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 5.15.194 / 6.1.153 / 6.6.107 or later
Fixed in 5.15.1946.1.1536.6.107
Vendor patch git.kernel.org →
Recommended fix High confidence

Kernel 5.15.194+ / 6.1.153+ / 6.6.107+ / 6.12.48+ depending on your current branch; Debian 11 requires upgrade to Debian 12 or equivalent patched kernel

  1. Identify the current kernel version by running `uname -r`
  2. Determine which version branch your kernel falls into based on the affected ranges: 4.19 to 5.15.x, 5.16 to 6.1.x, 6.2 to 6.6.x, or 6.7 to 6.12.x
  3. For 5.15.x kernels: upgrade to kernel version 5.15.194 or later
  4. For 6.1.x kernels: upgrade to kernel version 6.1.153 or later
  5. For 6.2-6.6.x kernels: upgrade to kernel version 6.6.107 or later
  6. For 6.7-6.12.x kernels: upgrade to kernel version 6.12.48 or later
  7. For Debian 11 systems: upgrade to Debian 12 (bookworm) or apply Debian-specific kernel security updates that include this fix
  8. Reboot the system into the updated kernel
Caveat Kernel upgrades may introduce regressions; ensure compatibility with custom drivers or modules before production deployment

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-2025-39873 in production — separate from our analysis above.

No notes yet

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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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