CVE-2025-40138Public exploit

Kernel crash via unchecked quota-name pointers

Published Nov 12, 2025 · Updated May 11, 2026

NULL pointer dereference in Linux kernel F2FS 6.17 through 6.17.2 allows local users to crash the kernel during a quota remount. The quota-consistency path passes an absent old_qname or new_qname pointer to strcmp() before validating both pointers. Reaching the remount path requires CAP_SYS_ADMIN in the initial user namespace, and the resulting NULL dereference interrupts the host.

CVSS severityUnavailable
Unscored
EPSS probability0.18%
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 Linux kernel F2FS 6.17 through 6.17.2 allows local users to crash the kernel during a quota remount. The quota-consistency path passes an absent old_qname or new_qname pointer to strcmp() before validating both pointers. Reaching the remount path requires CAP_SYS_ADMIN in the initial user namespace, and the resulting NULL dereference interrupts the host.

The record

CVE
CVE-2025-40138
Published
Nov 12, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Nov 12, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=6.17
  2. Affected versionversion=d185351325237da688de006a2c579e82ea97bdfe <3f3458852bbfe79c60f2412b8b04677b96688b6e
  3. Affected versionversion=d185351325237da688de006a2c579e82ea97bdfe <930a9a6ee8e7ffa20af4bffbfc2bbd21d83bf81c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=6.17; version=d185351325237da688de006a2c579e82ea97bdfe <3f3458852bbfe79c60f2412b8b04677b96688b6e; version=d185351325237da688de006a2c579e82ea97bdfe <930a9a6ee8e7ffa20af4bffbfc2bbd21d83bf81c

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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

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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