CVE-2025-39993

Kernel use-after-free via iMON disconnect race

Published Oct 15, 2025 · Updated Oct 15, 2025

A use-after-free in the Linux iMON driver from 2.6.35 allows local users to access a freed USB device during concurrent disconnect. imon_disconnect unconditionally drops the usb_device reference while usbdev_intf0 and usbdev_intf1 remain outside the users counter, letting writer paths dereference the released pointer. Access requires an active local writer path and concurrent iMON USB disconnect; the demonstrated consequence is an invalid kernel-memory read.

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

What happened

A use-after-free in the Linux iMON driver from 2.6.35 allows local users to access a freed USB device during concurrent disconnect. imon_disconnect unconditionally drops the usb_device reference while usbdev_intf0 and usbdev_intf1 remain outside the users counter, letting writer paths dereference the released pointer. Access requires an active local writer path and concurrent iMON USB disconnect; the demonstrated consequence is an invalid kernel-memory read.

The record

CVE
CVE-2025-39993
Published
Oct 15, 2025
Updated
Oct 15, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 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=21677cfc562a27e099719d413287bc8d1d24deb7 <2e7fd93b9cc565b839bc55a6662475718963e156
  2. Affected versionversion=21677cfc562a27e099719d413287bc8d1d24deb7 <71096a6161a25e84acddb89a9d77f138502d26ab
  3. Affected versionversion=21677cfc562a27e099719d413287bc8d1d24deb7 <71da40648741d15b302700b68973fe8b382aef3c
  4. Affected versionversion=21677cfc562a27e099719d413287bc8d1d24deb7 <d9f6ce99624a41c3bcb29a8d7d79b800665229dd
  5. Affected versionversion=21677cfc562a27e099719d413287bc8d1d24deb7 <fa0f61cc1d828178aa921475a9b786e7fbb65ccb
  6. Affected versionversion=21677cfc562a27e099719d413287bc8d1d24deb7 <fd5d3e6b149ec8cce045d86a2b5e3664d6b32ba5
  7. Affected versionversion=2.6.35

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=21677cfc562a27e099719d413287bc8d1d24deb7 <2e7fd93b9cc565b839bc55a6662475718963e156; version=21677cfc562a27e099719d413287bc8d1d24deb7 <71096a6161a25e84acddb89a9d77f138502d26ab; version=21677cfc562a27e099719d413287bc8d1d24deb7 <71da40648741d15b302700b68973fe8b382aef3c; version=21677cfc562a27e099719d413287bc8d1d24deb7 <d9f6ce99624a41c3bcb29a8d7d79b800665229dd; version=21677cfc562a27e099719d413287bc8d1d24deb7 <fa0f61cc1d828178aa921475a9b786e7fbb65ccb; version=21677cfc562a27e099719d413287bc8d1d24deb7 <fd5d3e6b149ec8cce045d86a2b5e3664d6b32ba5; version=2.6.35

Published CVSS scores

7.8Linux kernel CNACVSS: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 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

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Your stack

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