CVE-2021-3612Public exploit

System crash via unvalidated joystick button map

Published Jul 9, 2021 · Updated Aug 3, 2024

Out-of-bounds write in Linux kernel joystick code before 5.9-rc1 allows local users to crash the system through JSIOCSBTNMAP. The joydev_handle_JSIOCSBTNMAP function validates a copied button map but then traverses the original user buffer, allowing unchecked values to index beyond joydev->keymap. Triggering it requires access to a /dev/input/js* device backed by CONFIG_INPUT_JOYDEV; the demonstrated consequence is an immediate kernel panic.

CVSS severity7.8
High
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Linux kernel joystick code before 5.9-rc1 allows local users to crash the system through JSIOCSBTNMAP. The joydev_handle_JSIOCSBTNMAP function validates a copied button map but then traverses the original user buffer, allowing unchecked values to index beyond joydev->keymap. Triggering it requires access to a /dev/input/js* device backed by CONFIG_INPUT_JOYDEV; the demonstrated consequence is an immediate kernel panic.

The record

CVE
CVE-2021-3612
Published
Jul 9, 2021
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-787, CWE-20, T1499.004, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=kernel 5.9-rc1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=kernel 5.9-rc1

Published CVSS scores

7.8UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NISTAV:L/AC:L/Au:N/C:C/I:C/A:C
7.8NISTCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-787Out-of-bounds Write
CWE-20Improper Input Validation
T1499.004Application or System Exploitation
T1068Exploitation for Privilege Escalation

Public exploit references

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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