CVE-2024-40920

Adjacent disclosure and interruption via VLAN-group race

Published Jul 12, 2024 · Updated Aug 5, 2026

Use-after-free in Linux kernel bridge MST code allows attackers to disclose kernel data or interrupt the host via adjacent traffic. br_mst_set_state reads the port VLAN group with a non-RCU helper while concurrent updates can replace and free that group, leaving bridge state processing to use stale memory. Reachability requires an MST-enabled bridge on the same Layer 2 segment; crafted STP BPDUs can drive state transitions without credentials.

CVSS severity7.1
High
EPSS probability0.42%
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 kernel bridge MST code allows attackers to disclose kernel data or interrupt the host via adjacent traffic. br_mst_set_state reads the port VLAN group with a non-RCU helper while concurrent updates can replace and free that group, leaving bridge state processing to use stale memory. Reachability requires an MST-enabled bridge on the same Layer 2 segment; crafted STP BPDUs can drive state transitions without credentials.

The record

CVE
CVE-2024-40920
Published
Jul 12, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 12, 2024CVE 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=3a7c1661ae1383364cd6092d851f5e5da64d476b <546ceb1dfdac866648ec959cbc71d9525bd73462
  2. Affected versionversion=4488617e5e995a09abe4d81add5fb165674edb59 <7caefa2771722e65496d85b62e1dc4442b7d1345
  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 <caaa2129784a04dcade0ea92c12e6ff90bbd23d8
  8. Affected versionversion=a2b01e65d9ba8af2bb086d3b7288ca53a07249ac
  9. Affected versionversion=e43dd2b1ec746e105b7db5f9ad6ef14685a615a4 <406bfc04b01ee47e4c626f77ecc7d9f85135b166

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3a7c1661ae1383364cd6092d851f5e5da64d476b <546ceb1dfdac866648ec959cbc71d9525bd73462; version=4488617e5e995a09abe4d81add5fb165674edb59 <7caefa2771722e65496d85b62e1dc4442b7d1345; 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 <caaa2129784a04dcade0ea92c12e6ff90bbd23d8; version=a2b01e65d9ba8af2bb086d3b7288ca53a07249ac; version=e43dd2b1ec746e105b7db5f9ad6ef14685a615a4 <406bfc04b01ee47e4c626f77ecc7d9f85135b166

Published CVSS scores

7.1Linux kernel CNACVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
7.8NIST NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1499.004Application or System Exploitation

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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