CVE-2021-47646

Host crash via stale BFQ queue pointer

Published Feb 26, 2025 · Updated Aug 11, 2026

Use-after-free in the BFQ I/O scheduler in the Linux kernel allows local users to crash the host through concurrent block I/O. A block-group change leaves last_bfqq_created referencing a freed bfq_queue, and a later queue-merge path dereferences that stale object. BFQ must be active for the affected storage device; the stale object causes a kernel crash or kernel-context memory corruption.

CVSS severity7.8
High
EPSS probability0.28%
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 BFQ I/O scheduler in the Linux kernel allows local users to crash the host through concurrent block I/O. A block-group change leaves last_bfqq_created referencing a freed bfq_queue, and a later queue-merge path dereferences that stale object. BFQ must be active for the affected storage device; the stale object causes a kernel crash or kernel-context memory corruption.

The record

CVE
CVE-2021-47646
Published
Feb 26, 2025
Updated
Aug 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 26, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 11, 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=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <15729ff8143f8135b03988a100a19e66d7cb7ecd
  2. Affected versionversion=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <4083925bd6dc89216d156474a8076feec904e607
  3. Affected versionversion=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <65d8a737452e88f251fe5d925371de6d606df613
  4. Affected versionversion=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <abc2129e646af7b43025d90a071f83043f1ae76c
  5. Affected versionversion=5.13

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <15729ff8143f8135b03988a100a19e66d7cb7ecd; version=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <4083925bd6dc89216d156474a8076feec904e607; version=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <65d8a737452e88f251fe5d925371de6d606df613; version=430a67f9d6169a7b3e328bceb2ef9542e4153c7c <abc2129e646af7b43025d90a071f83043f1ae76c; version=5.13

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

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

CWE-416Use After Free
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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