CVE-2020-25668Public exploit

Kernel-memory disclosure via unsynchronized virtual-console selection

Published May 26, 2021 · Updated Aug 4, 2024

Use-after-free in the Linux Kernel TTY driver 5.9.2 allows local users to disclose kernel memory through virtual-terminal ioctls. The FONTX ioctl path passes a console selected through the unsynchronized fg_console global into con_font_op while concurrent VT_ACTIVATE and VT_DISALLOCATE calls switch and free that console. Access to a TTY device is required; the stale access can disclose kernel memory, crash the system, or enable privilege escalation.

CVSS severity7.0
High
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux Kernel TTY driver 5.9.2 allows local users to disclose kernel memory through virtual-terminal ioctls. The FONTX ioctl path passes a console selected through the unsynchronized fg_console global into con_font_op while concurrent VT_ACTIVATE and VT_DISALLOCATE calls switch and free that console. Access to a TTY device is required; the stale access can disclose kernel memory, crash the system, or enable privilege escalation.

The record

CVE
CVE-2020-25668
Published
May 26, 2021
Updated
Aug 4, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-362, CWE-662
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=5.9.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.9.2

Published CVSS scores

7.0NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
6.9NVDAV:L/AC:M/Au:N/C:C/I:C/A:C

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 exploitPublished

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CWE-662Improper Synchronization

Public exploit references

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Technologies

Your stack

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Your stack

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