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CVE-2021-47646

7.8 · 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…

Published Feb 26, 2025CWE-416EPSS 0.28%

Overview

CVE-2021-47646 is a high-severity vulnerability. It was published on February 26, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecdRefgit.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607Refgit.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613Refgit.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47646?

CVE-2021-47646 is a high-severity vulnerability. It was published on February 26, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2021-47646?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-47646?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-47646?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47646 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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