CVE-2025-21970

System crash via stale mlx5 bridge work

Published Apr 1, 2025 · Updated Aug 5, 2026

NULL-pointer dereference in the Linux kernel beginning with 5.15 allows local users to crash systems during mlx5 bridge LAG removal. When one physical function is unloaded, mlx5_lag_is_shared_fdb returns false, so mlx5_esw_bridge_lag_rep_get returns NULL and stale FDB work continues against a destroyed bond netdev. Triggering the crash requires low-privilege local access and an mlx5 offloaded bridge with a bond or LAG whose upper interface is being removed.

CVSS severity5.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL-pointer dereference in the Linux kernel beginning with 5.15 allows local users to crash systems during mlx5 bridge LAG removal. When one physical function is unloaded, mlx5_lag_is_shared_fdb returns false, so mlx5_esw_bridge_lag_rep_get returns NULL and stale FDB work continues against a destroyed bond netdev. Triggering the crash requires low-privilege local access and an mlx5 offloaded bridge with a bond or LAG whose upper interface is being removed.

The record

CVE
CVE-2025-21970
Published
Apr 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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=5.15
  2. Affected versionversion=ff9b7521468bc2909293c1cda66a245a49688f6f <4b8eeed4fb105770ce6dc84a2c6ef953c7b71cbb
  3. Affected versionversion=ff9b7521468bc2909293c1cda66a245a49688f6f <5dd8bf6ab1d6db40f5d09603759fa88caec19e7f
  4. Affected versionversion=ff9b7521468bc2909293c1cda66a245a49688f6f <86ff45f5f61ae1d0d17f0f6d8797b052eacfd8f1
  5. Affected versionversion=ff9b7521468bc2909293c1cda66a245a49688f6f <bd7e3a42800743a7748c83243e4cafc1b995d4c4
  6. Affected versionversion=ff9b7521468bc2909293c1cda66a245a49688f6f <f7bf259a04271165ae667ad21cfc60c6413f25ca
  7. Affected versionversion=ff9b7521468bc2909293c1cda66a245a49688f6f <f90c4d6572488e2bad38cca00f1c59174a538a1a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.15; version=ff9b7521468bc2909293c1cda66a245a49688f6f <4b8eeed4fb105770ce6dc84a2c6ef953c7b71cbb; version=ff9b7521468bc2909293c1cda66a245a49688f6f <5dd8bf6ab1d6db40f5d09603759fa88caec19e7f; version=ff9b7521468bc2909293c1cda66a245a49688f6f <86ff45f5f61ae1d0d17f0f6d8797b052eacfd8f1; version=ff9b7521468bc2909293c1cda66a245a49688f6f <bd7e3a42800743a7748c83243e4cafc1b995d4c4; version=ff9b7521468bc2909293c1cda66a245a49688f6f <f7bf259a04271165ae667ad21cfc60c6413f25ca; version=ff9b7521468bc2909293c1cda66a245a49688f6f <f90c4d6572488e2bad38cca00f1c59174a538a1a

Published CVSS scores

5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0Oracle LinuxCVSS:3.1/AV:P/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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

CWE-476NULL Pointer Dereference
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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