CVE-2021-47646

High

In the Linux kernel, the following vulnerability has been resolved: Revert "Revert "block, bfq: honor already-setup queue merges"" A crash [1] happened to be triggered in conjunction with commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges"). The latter was then reverted by commit ebc69e897e17 ("Revert "block, bfq: honor already-setup queue merges""). Yet, the reverted commit was not the one introducing the bug. In fact, it actually triggered a UAF introduced by a different commit, and now fixed by commit d29bd41428cf ("block, bfq: reset last_bfqq_created on group change"). So, there is no point in keeping commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges") out. This commit restores it. [1] https://bugzilla.kernel.org/show_bug.cgi?id=214503

Package Linux Kernel
Published 2025-02-26
Last modified 2025-03-24
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

7.8

out of 10
High
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2021-47646 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 4.12 and later are affected. Fixed in 4.19.238, 5.4.189, 5.10.110, 5.15.33, 5.16.19, 5.17.2, 5.18 and their respective stable series.

Affected from
≥ 4.12
Fixed in
✓ 4.19.238 4.19.x ✓ 5.4.189 5.4.x ✓ 5.10.110 5.10.x ✓ 5.15.33 5.15.x ✓ 5.16.19 5.16.x ✓ 5.17.2 5.17.x ✓ 5.18

References

The following references provide additional information about CVE-2021-47646 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

7 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2021-47646?

    CVE-2021-47646 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 4.12 onward and has been patched in 4.19.238, 5.4.189, 5.10.110 and others. CVE-2021-47646 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2021-47646?

    CVE-2021-47646 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2021-47646?

    Yes — CVE-2021-47646 has been patched. Fixed versions include 4.19.238, 5.4.189, 5.10.110 and others. If you are running Linux kernel 4.12 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2021-47646 actively exploited?

    No — CVE-2021-47646 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Use After Free (CWE-416)?

    The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. View CWE-416 on MITRE CWE →

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