CVE-2025-40126

Local service interruption via incorrect copy accounting

Published Nov 12, 2025 · Updated May 23, 2026

Affected Linux kernel releases allow local users to disrupt system operations through faulting UltraSPARC user-memory copies. In arch/sparc/lib/U1memcpy.S, exception handlers calculate bytes remaining from incorrect register values, causing copy_from_user and copy_to_user to report wrong return counts after a fault. Low-privileged local execution on UltraSPARC is required, and callers can act on the incorrect partial-copy count, affecting data integrity or availability.

CVSS severity6.9
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Affected Linux kernel releases allow local users to disrupt system operations through faulting UltraSPARC user-memory copies. In arch/sparc/lib/U1memcpy.S, exception handlers calculate bytes remaining from incorrect register values, causing copy_from_user and copy_to_user to report wrong return counts after a fault. Low-privileged local execution on UltraSPARC is required, and callers can act on the incorrect partial-copy count, affecting data integrity or availability.

The record

CVE
CVE-2025-40126
Published
Nov 12, 2025
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 12, 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

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=1731d90d8a558ecb20cdee0c2c001ae8e15c251d
  2. Affected versionversion=4.4.34 <4.5
  3. Affected versionversion=4.8.10 <4.9
  4. Affected versionversion=4.9
  5. Affected versionversion=b0580eadc19ff3a617a7d07cfaf2a985153c114e
  6. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <0bf3dc3a2156f1c5ddaba4b85d09767874634114
  7. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <41c18baee66134e6ef786eb075c1b6adb22432b0
  8. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <4fba1713001195e59cfc001ff1f2837dab877efb
  9. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <57c278500fce3cd4e1c540700c0b05426a958393
  10. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <59424dc0d0e044b2eb007686a4724ddd91d57db5
  11. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <674ff598148a28bae0b5372339de56f2abf0b1d1
  12. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <7de3a75bbc8465d816336c74d50109e73501efab
  13. Affected versionversion=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <9b137f277cc3297044aabd950f589e505d30104c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1731d90d8a558ecb20cdee0c2c001ae8e15c251d; version=4.4.34 <4.5; version=4.8.10 <4.9; version=4.9; version=b0580eadc19ff3a617a7d07cfaf2a985153c114e; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <0bf3dc3a2156f1c5ddaba4b85d09767874634114; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <41c18baee66134e6ef786eb075c1b6adb22432b0; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <4fba1713001195e59cfc001ff1f2837dab877efb; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <57c278500fce3cd4e1c540700c0b05426a958393; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <59424dc0d0e044b2eb007686a4724ddd91d57db5; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <674ff598148a28bae0b5372339de56f2abf0b1d1; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <7de3a75bbc8465d816336c74d50109e73501efab; version=cb736fdbb208eb3420f1a2eb2bfc024a6e9dcada <9b137f277cc3297044aabd950f589e505d30104c

Published CVSS scores

6.1SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
6.9SUSECVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N

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

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

See the directory against your own environment.

Your stack

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