CVE-2026-98301

Kernel RCU violation via blocking MST notifier

Published Oct 6, 2026 · Updated Oct 6, 2026

Improper blocking in Linux bridge MST handling allows local users with network-administration privileges to trigger an RCU violation via netlink. In br_mst_set_state(), a nonzero MSTI update calls switchdev_port_attr_set() while rcu_read_lock() is held, although the blocking notifier chain can sleep. The path requires a nonzero MSTI change through bridge netlink; the upstream patch does not establish a specific crash, hang, or data-access outcome.

CVSS severityUnavailable
Unscored
EPSS probability0.18%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper blocking in Linux bridge MST handling allows local users with network-administration privileges to trigger an RCU violation via netlink. In br_mst_set_state(), a nonzero MSTI update calls switchdev_port_attr_set() while rcu_read_lock() is held, although the blocking notifier chain can sleep. The path requires a nonzero MSTI change through bridge netlink; the upstream patch does not establish a specific crash, hang, or data-access outcome.

The record

CVE
CVE-2026-98301
Published
Oct 6, 2026
Updated
Oct 6, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Oct 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 6, 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 <18a6fe05fb6e18de29fa90d388bb34044114b3d8
  2. Affected versionversion=3a7c1661ae1383364cd6092d851f5e5da64d476b <abf734d150c61acfdfee102169d0e5d1c482e285
  3. Affected versionversion=3a7c1661ae1383364cd6092d851f5e5da64d476b <c40ed3e884c8dc0350f26484030438ef24208ff1
  4. Affected versionversion=3a7c1661ae1383364cd6092d851f5e5da64d476b <d5c4ee1fa4e83a12afc051c831936cd8e006cde3
  5. Affected versionversion=4488617e5e995a09abe4d81add5fb165674edb59 <6b431b63219853eef4054e2f1cb073d2ca2059b4
  6. Affected versionversion=6.10
  7. Affected versionversion=6.1.93 <6.1.189
  8. Affected versionversion=6.6.33 <6.6.158
  9. Affected versionversion=6.8.12 <6.9
  10. Affected versionversion=6.9.3 <6.10
  11. Affected versionversion=8ca9a750fc711911ef616ceb627d07357b04545e <b9661fd2423fc25e91e0517ecc0b6156ad83e3a8
  12. Affected versionversion=a2b01e65d9ba8af2bb086d3b7288ca53a07249ac
  13. Affected versionversion=e43dd2b1ec746e105b7db5f9ad6ef14685a615a4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=3a7c1661ae1383364cd6092d851f5e5da64d476b <18a6fe05fb6e18de29fa90d388bb34044114b3d8; version=3a7c1661ae1383364cd6092d851f5e5da64d476b <abf734d150c61acfdfee102169d0e5d1c482e285; version=3a7c1661ae1383364cd6092d851f5e5da64d476b <c40ed3e884c8dc0350f26484030438ef24208ff1; version=3a7c1661ae1383364cd6092d851f5e5da64d476b <d5c4ee1fa4e83a12afc051c831936cd8e006cde3; version=4488617e5e995a09abe4d81add5fb165674edb59 <6b431b63219853eef4054e2f1cb073d2ca2059b4; version=6.10; version=6.1.93 <6.1.189; version=6.6.33 <6.6.158; version=6.8.12 <6.9; version=6.9.3 <6.10; version=8ca9a750fc711911ef616ceb627d07357b04545e <b9661fd2423fc25e91e0517ecc0b6156ad83e3a8; version=a2b01e65d9ba8af2bb086d3b7288ca53a07249ac; version=e43dd2b1ec746e105b7db5f9ad6ef14685a615a4

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

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No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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