CVE-2024-40921

Kernel availability loss via redundant VLAN-group dereference

Published Jul 12, 2024 · Updated May 23, 2026

Improper pointer handling in affected Linux kernel versions allows local users to interrupt kernel availability through bridge MST state changes. In net/bridge/br_mst.c, br_mst_vlan_set_state() reacquires and dereferences a VLAN-group pointer even though its callers already hold the correctly dereferenced group in their RCU context. Low-privileged local access and a bridge using Multiple Spanning Tree state are required, and the documented impact is limited to availability.

CVSS severity5.5
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper pointer handling in affected Linux kernel versions allows local users to interrupt kernel availability through bridge MST state changes. In net/bridge/br_mst.c, br_mst_vlan_set_state() reacquires and dereferences a VLAN-group pointer even though its callers already hold the correctly dereferenced group in their RCU context. Low-privileged local access and a bridge using Multiple Spanning Tree state are required, and the documented impact is limited to availability.

The record

CVE
CVE-2024-40921
Published
Jul 12, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 12, 2024CVE publishedPublication date reported by the CVE source.
  2. May 23, 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=3a7c1661ae1383364cd6092d851f5e5da64d476b <36c92936e868601fa1f43da6758cf55805043509
  2. Affected versionversion=4488617e5e995a09abe4d81add5fb165674edb59 <a6cc9e9a651b9861efa068c164ee62dfba68c6ca
  3. Affected versionversion=6.1.93 <6.1.95
  4. Affected versionversion=6.6.33 <6.6.35
  5. Affected versionversion=6.8.12 <6.9
  6. Affected versionversion=6.9.3 <6.9.6
  7. Affected versionversion=8ca9a750fc711911ef616ceb627d07357b04545e <09f4337c27f5bdeb8646a6db91488cc2f7d537ff
  8. Affected versionversion=a2b01e65d9ba8af2bb086d3b7288ca53a07249ac
  9. Affected versionversion=e43dd2b1ec746e105b7db5f9ad6ef14685a615a4 <d2dc02775fc0c4eacaee833a0637e5958884a8e5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3a7c1661ae1383364cd6092d851f5e5da64d476b <36c92936e868601fa1f43da6758cf55805043509; version=4488617e5e995a09abe4d81add5fb165674edb59 <a6cc9e9a651b9861efa068c164ee62dfba68c6ca; version=6.1.93 <6.1.95; version=6.6.33 <6.6.35; version=6.8.12 <6.9; version=6.9.3 <6.9.6; version=8ca9a750fc711911ef616ceb627d07357b04545e <09f4337c27f5bdeb8646a6db91488cc2f7d537ff; version=a2b01e65d9ba8af2bb086d3b7288ca53a07249ac; version=e43dd2b1ec746e105b7db5f9ad6ef14685a615a4 <d2dc02775fc0c4eacaee833a0637e5958884a8e5

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CanonicalCVSS:3.1/AV:L/AC:L/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

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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