CVE-2025-39684

Kernel-memory disclosure via partially initialized Comedi buffers

Published Sep 5, 2025 · Updated Sep 5, 2025

Information disclosure in the Linux Comedi ioctl path allows local users to read uninitialized kernel memory through crafted instructions. The do_insn_ioctl() and do_insnlist_ioctl() paths copy insn->n samples to user space even when handlers such as insn_rw_emulate_bits() initialize fewer samples. A local user who can open an affected Comedi device can recover residual kernel data, with no reported write or code-execution impact.

CVSS severity5.5
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Linux Comedi ioctl path allows local users to read uninitialized kernel memory through crafted instructions. The do_insn_ioctl() and do_insnlist_ioctl() paths copy insn->n samples to user space even when handlers such as insn_rw_emulate_bits() initialize fewer samples. A local user who can open an affected Comedi device can recover residual kernel data, with no reported write or code-execution impact.

The record

CVE
CVE-2025-39684
Published
Sep 5, 2025
Updated
Sep 5, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 5, 2025Record 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=2.6.29
  2. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <3cd212e895ca2d58963fdc6422502b10dd3966bb
  3. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <868a1b68dcd9f2805bb86aa64862402f785d8c4a
  4. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <aecf0d557ddd95ce68193a5ee1dc4c87415ff08a
  5. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <d84f6e77ebe3359394df32ecd97e0d76a25283dc
  6. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <f3b0c9ec54736f3b8118f93a473d22e11ee65743
  7. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <ff4a7c18799c7fe999fa56c5cf276e13866b8c1a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.29; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <3cd212e895ca2d58963fdc6422502b10dd3966bb; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <868a1b68dcd9f2805bb86aa64862402f785d8c4a; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <aecf0d557ddd95ce68193a5ee1dc4c87415ff08a; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <d84f6e77ebe3359394df32ecd97e0d76a25283dc; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <f3b0c9ec54736f3b8118f93a473d22e11ee65743; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <ff4a7c18799c7fe999fa56c5cf276e13866b8c1a

Published CVSS scores

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

T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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