CVE-2021-28964

System crash via unlocked extent-buffer cloning

Published Mar 22, 2021 · Updated Aug 3, 2024

Race condition in Btrfs in the Linux kernel through 5.11.8 allows local users to crash the system during concurrent cloning operations. get_old_root clones an extent buffer without first taking its lock, allowing concurrent tree modification to violate Btrfs consistency checks. A local user able to trigger concurrent Btrfs cloning can reach the race; the documented consequence is a kernel BUG and system crash, not data access or code execution.

CVSS severity4.7
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Btrfs in the Linux kernel through 5.11.8 allows local users to crash the system during concurrent cloning operations. get_old_root clones an extent buffer without first taking its lock, allowing concurrent tree modification to violate Btrfs consistency checks. A local user able to trigger concurrent Btrfs cloning can reach the race; the documented consequence is a kernel BUG and system crash, not data access or code execution.

The record

CVE
CVE-2021-28964
Published
Mar 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-362, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 22, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

1.9NIST NVDAV:L/AC:M/Au:N/C:N/I:N/A:P
4.7NIST NVDCVSS:3.1/AV:L/AC:H/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation

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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