CVE-2021-3739

System crash via invalid BTRFS device removal

Published Mar 7, 2022 · Updated Aug 3, 2024

NULL pointer dereference in Linux Kernel BTRFS before 5.15-rc1 allows local users with CAP_SYS_ADMIN to crash the system. The BTRFS_IOC_RM_DEV_V2 path accepts a nonexistent device ID, and btrfs_rm_device dereferences the resulting null device pointer. Exploitation requires local CAP_SYS_ADMIN access and a BTRFS filesystem; the documented security consequence is a host crash, while the source record also reports possible kernel-information disclosure.

CVSS severity7.1
High
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Linux Kernel BTRFS before 5.15-rc1 allows local users with CAP_SYS_ADMIN to crash the system. The BTRFS_IOC_RM_DEV_V2 path accepts a nonexistent device ID, and btrfs_rm_device dereferences the resulting null device pointer. Exploitation requires local CAP_SYS_ADMIN access and a BTRFS filesystem; the documented security consequence is a host crash, while the source record also reports possible kernel-information disclosure.

The record

CVE
CVE-2021-3739
Published
Mar 7, 2022
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-476
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 7, 2022CVE 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=Fixed in v5.15-rc1 and above.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=Fixed in v5.15-rc1 and above.

Published CVSS scores

7.1NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
3.6NVDAV:L/AC:L/Au:N/C:P/I:N/A:P
4.4SUSECVSS:3.1/AV:L/AC:L/PR:H/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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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