CVE-2025-39989

Local denial of service via misclassified poisoned-memory access

Published Apr 18, 2025 · Updated May 23, 2026

Denial of service in affected Linux kernel versions allows local users to cause a kernel panic through hardware-poisoned user memory. The x86 machine-check handler recognizes only EX_TYPE_UACCESS as a recoverable copy-from-user context, so newer EX_TYPE_EFAULT_REG fixups are misclassified instead of returning EFAULT. Reaching the flaw requires a poisoned user page during a copy operation; a related CMCI/MCE race during instruction fetch can instead terminate the affected process with SIGBUS.

CVSS severity5.5
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Linux kernel versions allows local users to cause a kernel panic through hardware-poisoned user memory. The x86 machine-check handler recognizes only EX_TYPE_UACCESS as a recoverable copy-from-user context, so newer EX_TYPE_EFAULT_REG fixups are misclassified instead of returning EFAULT. Reaching the flaw requires a poisoned user page during a copy operation; a related CMCI/MCE race during instruction fetch can instead terminate the affected process with SIGBUS.

The record

CVE
CVE-2025-39989
Published
Apr 18, 2025
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 18, 2025CVE publishedPublication date reported by the CVE source.
  2. May 23, 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=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <0b8388e97ba6a8c033f9a8b5565af41af07f9345
  2. Affected versionversion=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <1a15bb8303b6b104e78028b6c68f76a0d4562134
  3. Affected versionversion=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <3e3d8169c0950a0b3cd5105f6403a78350dcac80
  4. Affected versionversion=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <449413da90a337f343cc5a73070cbd68e92e8a54
  5. Affected versionversion=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <5724654a084f701dc64b08d34a0e800f22f0e6e4
  6. Affected versionversion=5.15.58 <5.16
  7. Affected versionversion=5.17
  8. Affected versionversion=88eded8104d2ca0429703755dd250f8cbecc1447

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <0b8388e97ba6a8c033f9a8b5565af41af07f9345; version=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <1a15bb8303b6b104e78028b6c68f76a0d4562134; version=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <3e3d8169c0950a0b3cd5105f6403a78350dcac80; version=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <449413da90a337f343cc5a73070cbd68e92e8a54; version=4c132d1d844a53fc4e4b5c34e36ef10d6124b783 <5724654a084f701dc64b08d34a0e800f22f0e6e4; version=5.15.58 <5.16; version=5.17; version=88eded8104d2ca0429703755dd250f8cbecc1447

Published CVSS scores

5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application 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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Your stack

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