CVE-2025-40203

Kernel-memory corruption via mount-reference race

Published Nov 12, 2025 · Updated Aug 5, 2026

A reference-count race in fs/namespace.c in affected Linux kernel builds from 6.8 allows local users to corrupt kernel memory through listmount. do_listmount calls path_put while holding namespace_sem, so a sibling thread can move the shared root and make that release free mount objects during protected traversal. An unprivileged user namespace supplies the required mount operations; exploitation can hijack control flow, oops the kernel, or hang systemwide mount operations.

CVSS severity7.8
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A reference-count race in fs/namespace.c in affected Linux kernel builds from 6.8 allows local users to corrupt kernel memory through listmount. do_listmount calls path_put while holding namespace_sem, so a sibling thread can move the shared root and make that release free mount objects during protected traversal. An unprivileged user namespace supplies the required mount operations; exploitation can hijack control flow, oops the kernel, or hang systemwide mount operations.

The record

CVE
CVE-2025-40203
Published
Nov 12, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 12, 2025CVE 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.8
  2. Affected versionversion=b4c2bea8ceaa50cd42a8f73667389d801a3ecf2d <659874b7ee4976ad9ce476e07fd36bc67b3537f1
  3. Affected versionversion=b4c2bea8ceaa50cd42a8f73667389d801a3ecf2d <9c80da26fda2fdcaac7f92b5908875b3108830ff
  4. Affected versionversion=b4c2bea8ceaa50cd42a8f73667389d801a3ecf2d <c1f86d0ac322c7e77f6f8dbd216c65d39358ffc0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.8; version=b4c2bea8ceaa50cd42a8f73667389d801a3ecf2d <659874b7ee4976ad9ce476e07fd36bc67b3537f1; version=b4c2bea8ceaa50cd42a8f73667389d801a3ecf2d <9c80da26fda2fdcaac7f92b5908875b3108830ff; version=b4c2bea8ceaa50cd42a8f73667389d801a3ecf2d <c1f86d0ac322c7e77f6f8dbd216c65d39358ffc0

Published CVSS scores

7.8LinuxCVSS: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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service
T1068Exploitation for Privilege Escalation

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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