CVE-2025-39855

High

In the Linux kernel, the following vulnerability has been resolved: ice: fix NULL access of tx->in_use in ice_ptp_ts_irq The E810 device has support for a "low latency" firmware interface to access and read the Tx timestamps. This interface does not use the standard Tx timestamp logic, due to the latency overhead of proxying sideband command requests over the firmware AdminQ. The logic still makes use of the Tx timestamp tracking structure, ice_ptp_tx, as it uses the same "ready" bitmap to track which Tx timestamps complete. Unfortunately, the ice_ptp_ts_irq() function does not check if the tracker is initialized before its first access. This results in NULL dereference or use-after-free bugs similar to the following: [245977.278756] BUG: kernel NULL pointer dereference, address: 0000000000000000 [245977.278774] RIP: 0010:_find_first_bit+0x19/0x40 [245977.278796] Call Trace: [245977.278809] ? ice_misc_intr+0x364/0x380 [ice] This can occur if a Tx timestamp interrupt races with the driver reset logic. Fix this by only checking the in_use bitmap (and other fields) if the tracker is marked as initialized. The reset flow will clear the init field under lock before it tears the tracker down, thus preventing any use-after-free or NULL access.

Package Linux Kernel
Published 2025-09-19
Last modified 2026-01-14
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

7.8

out of 10
High
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2025-39855 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.15 and later are affected. Fixed in 6.16.6, 6.17 and their respective stable series.

Affected from
≥ 6.15
Fixed in
✓ 6.16.6 6.16.x ✓ 6.17

References

The following references provide additional information about CVE-2025-39855 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Frequently asked questions

  • What is CVE-2025-39855?

    CVE-2025-39855 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 6.15 onward and has been patched in 6.16.6 and 6.17. CVE-2025-39855 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-39855?

    CVE-2025-39855 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2025-39855?

    Yes — CVE-2025-39855 has been patched. Fixed versions include 6.16.6 and 6.17. If you are running Linux kernel 6.15 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-39855 actively exploited?

    No — CVE-2025-39855 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Use After Free (CWE-416)?

    The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. View CWE-416 on MITRE CWE →

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