CVE-2021-47189

Kernel crash via unordered btrfs work completion

Published Apr 10, 2024 · Updated Aug 5, 2026

Race condition in affected Linux btrfs kernels allows local users to crash the kernel through concurrent compressed writeback. In fs/btrfs/async-thread.c, ordinary bit operations on WORK_DONE_BIT provide no memory ordering, so run_ordered_work can observe async_chunk state before producer writes are visible. A local user needs write access to a mounted btrfs filesystem and can trigger the race with ordinary writes and fsync; the resulting stale or torn state can cause an oops, hang, memory disclosure, or memory corruption.

CVSS severity7.8
High
EPSS probability0.66%
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 affected Linux btrfs kernels allows local users to crash the kernel through concurrent compressed writeback. In fs/btrfs/async-thread.c, ordinary bit operations on WORK_DONE_BIT provide no memory ordering, so run_ordered_work can observe async_chunk state before producer writes are visible. A local user needs write access to a mounted btrfs filesystem and can trigger the race with ordinary writes and fsync; the resulting stale or torn state can cause an oops, hang, memory disclosure, or memory corruption.

The record

CVE
CVE-2021-47189
Published
Apr 10, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 10, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record 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=08a9ff3264181986d1d692a4e6fce3669700c9f8 <45da9c1767ac31857df572f0a909fbe88fd5a7e9
  2. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <47e6f9f69153247109042010f3a77579e9dc61ff
  3. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <637d652d351fd4f263ef302dc52f3971d314e500
  4. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <670f6b3867c8f0f11e5097f353b164cecfec6179
  5. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <6adbc07ebcaf8bead08b21687d49e0fc94400987
  6. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <804a9d239ae9cbe88e861a7cd62319cc6ec7b136
  7. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <bd660a20fea3ec60a49709ef5360f145ec0fe779
  8. Affected versionversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <ed058d735a70f4b063323f1a7bb33cda0f987513
  9. Affected versionversion=3.15

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=08a9ff3264181986d1d692a4e6fce3669700c9f8 <45da9c1767ac31857df572f0a909fbe88fd5a7e9; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <47e6f9f69153247109042010f3a77579e9dc61ff; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <637d652d351fd4f263ef302dc52f3971d314e500; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <670f6b3867c8f0f11e5097f353b164cecfec6179; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <6adbc07ebcaf8bead08b21687d49e0fc94400987; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <804a9d239ae9cbe88e861a7cd62319cc6ec7b136; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <bd660a20fea3ec60a49709ef5360f145ec0fe779; version=08a9ff3264181986d1d692a4e6fce3669700c9f8 <ed058d735a70f4b063323f1a7bb33cda0f987513; version=3.15

Published CVSS scores

7.8Linux Kernel CVE TeamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

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 exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

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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