CVE-2021-47412

Host crash via untracked bio completion callback

Published May 21, 2024 · Updated Aug 5, 2026

Use-after-free in the Linux kernel block layer allows local users to crash the host through concurrent I/O and device teardown. In bio_endio(), rq_qos_done_bio() follows bio->bi_bdev to a request queue and invokes rq_qos_ops->done_bio even when the bio was never tracked, after queue cleanup can free q->rq_qos. Reachability requires local access to issue block I/O while inducing device or queue teardown; successful exploitation can panic the kernel and interrupt the host.

CVSS severity5.5
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

Use-after-free in the Linux kernel block layer allows local users to crash the host through concurrent I/O and device teardown. In bio_endio(), rq_qos_done_bio() follows bio->bi_bdev to a request queue and invokes rq_qos_ops->done_bio even when the bio was never tracked, after queue cleanup can free q->rq_qos. Reachability requires local access to issue block I/O while inducing device or queue teardown; successful exploitation can panic the kernel and interrupt the host.

The record

CVE
CVE-2021-47412
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=4.19
  2. Affected versionversion=67b42d0bf7a8fd1ec0cf1acdc9550e688d7c8578 <004b8f8a691205a93d9e80d98b786b2b97424d6e
  3. Affected versionversion=67b42d0bf7a8fd1ec0cf1acdc9550e688d7c8578 <a647a524a46736786c95cdb553a070322ca096e3
  4. Affected versionversion=67b42d0bf7a8fd1ec0cf1acdc9550e688d7c8578 <db60edbfff332a6a5477c367af8125f034570989

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.19; version=67b42d0bf7a8fd1ec0cf1acdc9550e688d7c8578 <004b8f8a691205a93d9e80d98b786b2b97424d6e; version=67b42d0bf7a8fd1ec0cf1acdc9550e688d7c8578 <a647a524a46736786c95cdb553a070322ca096e3; version=67b42d0bf7a8fd1ec0cf1acdc9550e688d7c8578 <db60edbfff332a6a5477c367af8125f034570989

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/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.

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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

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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