CVE-2021-47646

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2025-02-27. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0

A fix is available — apply it.

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

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
35(Track)
EG Risk 35/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
20%
KEV
Not listed

Published

February 26, 2025

Last Modified

August 5, 2026

Advisory Details (7)

Auto-updated Aug 5, 2026
No patch confirmed yet.
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/cc051f497eac9d8a0d816cd4bffa3415f2724871
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/931aff627469a75c77b9fd3823146d0575afffd6
generic

Revert "Revert "block, bfq: honor already-setup queue merges"" - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f990f0985eda59d4f29fc83fcf300c92b1225d39

Vendor Advisories for CVE-2021-47646(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatkernel-0:5.14.0-162.6.1.el9_12022-11-15redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 115 total refreshes for this CVE.

  1. 2026-08-07 16:24 UTCEPSS rescore
  2. 2026-08-06 13:44 UTCEPSS rescore
  3. 2026-08-05 19:15 UTCEPSS rescore
  4. 2026-08-05 09:35 UTCEG score recompute
  5. 2026-08-05 09:35 UTCVendor advisory
  6. 2026-08-05 09:35 UTCGHSA enrichment
  7. 2026-08-04 15:06 UTCEPSS rescore
  8. 2026-08-04 10:34 UTCEPSS rescore
  9. 2026-08-04 09:47 UTCEG score recompute
  10. 2026-08-04 09:47 UTCVendor advisory
  11. 2026-08-04 09:47 UTCGHSA enrichment
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  23. 2026-07-23 09:19 UTCOSV refresh
  24. 2026-07-23 02:06 UTCEG score recompute
  25. 2026-07-22 22:53 UTCEG score recompute
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  1. 2026-07-22 14:06 UTCEPSS rescore
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  23. 2026-07-07 13:43 UTCEPSS rescore
  24. 2026-07-06 16:25 UTCEPSS rescore
  25. 2026-07-06 16:25 UTCEPSS rescore
  26. 2026-07-06 04:32 UTCOSV refresh
  27. 2026-07-06 02:21 UTCEPSS rescore
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  54. 2026-06-18 17:51 UTCEPSS rescore
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  56. 2026-06-17 15:35 UTCOSV refresh
  57. 2026-06-16 17:51 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-47646?
CVE-2021-47646 is a high vulnerability published on February 26, 2025. 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…
When was CVE-2021-47646 disclosed?
CVE-2021-47646 was first published in the National Vulnerability Database on February 26, 2025, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-47646 actively exploited?
CVE-2021-47646 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 79.5% of all scored CVEs.
What is the CVSS score of CVE-2021-47646?
CVE-2021-47646 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2021-47646?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-47646, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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