CVE-2021-20261

System crash via interrupted floppy-driver lock

Published Mar 11, 2021 · Updated Aug 3, 2024

A race condition in the Linux Kernel 5.12-rc2 floppy driver allows local users with device access to crash the system. The floppy_revalidate and floppy_check_events paths ignore an interrupted lock_fdc return and continue without the lockedfd critical-section guard. Access to /dev/fd0 requires root-equivalent permissions by default; relaxed device permissions expose memory corruption and possible privilege escalation.

CVSS severity6.4
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A race condition in the Linux Kernel 5.12-rc2 floppy driver allows local users with device access to crash the system. The floppy_revalidate and floppy_check_events paths ignore an interrupted lock_fdc return and continue without the lockedfd critical-section guard. Access to /dev/fd0 requires root-equivalent permissions by default; relaxed device permissions expose memory corruption and possible privilege escalation.

The record

CVE
CVE-2021-20261
Published
Mar 11, 2021
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-362, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 11, 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 5.12-rc2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=kernel 5.12-rc2

Published CVSS scores

6.4NIST NVDCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
4.4NIST NVDAV:L/AC:M/Au:N/C:P/I:P/A:P

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1068Exploitation for Privilege Escalation

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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