CVE-2025-39979

Kernel crash via uninitialized flow-counter references

Published Oct 15, 2025 · Updated Aug 5, 2026

Use-after-free in Linux 6.14 mlx5 flow steering allows local users to crash the kernel by deleting an RDMA flow rule. mlx5_cmd_hws_delete_fte() releases an HWS action for a local flow counter whose mutex and reference count were never initialized, after the counter can already be freed. Triggering the faulty teardown requires low-privileged local access to the RDMA userspace verbs interface and an mlx5 device using hardware steering.

CVSS severity7.8
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux 6.14 mlx5 flow steering allows local users to crash the kernel by deleting an RDMA flow rule. mlx5_cmd_hws_delete_fte() releases an HWS action for a local flow counter whose mutex and reference count were never initialized, after the counter can already be freed. Triggering the faulty teardown requires low-privileged local access to the RDMA userspace verbs interface and an mlx5 device using hardware steering.

The record

CVE
CVE-2025-39979
Published
Oct 15, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.14
  2. Affected versionversion=b581f4266928d3b5d1bbe711e39623d9a1696091 <3c77f6d244188c3fb11f6aec40bbfe884f1803b5
  3. Affected versionversion=b581f4266928d3b5d1bbe711e39623d9a1696091 <6043819e707cefb1c9e59d6e431dcfa735c4f975

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.14; version=b581f4266928d3b5d1bbe711e39623d9a1696091 <3c77f6d244188c3fb11f6aec40bbfe884f1803b5; version=b581f4266928d3b5d1bbe711e39623d9a1696091 <6043819e707cefb1c9e59d6e431dcfa735c4f975

Published CVSS scores

7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.6OracleCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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