CVE-2026-99174

Kernel crash via premature ext4 state release

Published Oct 28, 2026 · Updated Oct 28, 2026

A teardown race in Linux ext4 allows local users to crash the kernel via symlink lookup racing final mount-reference release. ext4_put_super() clears and frees superblock-private state and destroys counters while ext4_get_link() still accesses them during RCU pathwalk. The race requires final mount-reference release outside ordinary unmount, such as closing a file on a lazily unmounted filesystem; the reported result is a kernel null-pointer fault.

CVSS severityUnavailable
Unscored
EPSS probability0.18%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A teardown race in Linux ext4 allows local users to crash the kernel via symlink lookup racing final mount-reference release. ext4_put_super() clears and frees superblock-private state and destroys counters while ext4_get_link() still accesses them during RCU pathwalk. The race requires final mount-reference release outside ordinary unmount, such as closing a file on a lazily unmounted filesystem; the reported result is a kernel null-pointer fault.

The record

CVE
CVE-2026-99174
Published
Oct 28, 2026
Updated
Oct 28, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Oct 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 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=5.19
  2. Affected versionversion=6493792d3299b3e33f887ef8a150099d271faf9c <80d5db1686b05fad6f384be017714297d828a714
  3. Affected versionversion=6493792d3299b3e33f887ef8a150099d271faf9c <87d29b8b849738d52fe820d495fa0aa2d5a1ec82
  4. Affected versionversion=6493792d3299b3e33f887ef8a150099d271faf9c <c17b44266a1f9fcb49b894d4611d1254bf1aa313

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=5.19; version=6493792d3299b3e33f887ef8a150099d271faf9c <80d5db1686b05fad6f384be017714297d828a714; version=6493792d3299b3e33f887ef8a150099d271faf9c <87d29b8b849738d52fe820d495fa0aa2d5a1ec82; version=6493792d3299b3e33f887ef8a150099d271faf9c <c17b44266a1f9fcb49b894d4611d1254bf1aa313

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
PrivilegesUnavailable
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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