7.8

CVE-2021-47646: Revert "Revert "block, bfq: honor already-setup queue merges""

Modified
AliasesUBUNTU-CVE-2021-47646DEBIAN-CVE-2021-47646
Published 26-02-2025Last modified 11-08-2026

Vulnerability summary

CVE-2021-47646 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 20.9% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.8/10
010
High · v3.1 (CVE.org)
EPSS score
0.28%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 5 · Related 4
RHSA-2022:8267SUSE-SU-2025:1027-1SUSE-SU-2025:1176-1SUSE-SU-2025:1183-1SUSE-SU-2025:1241-1

Timeline

  1. 26-02-2025
    PublishedVulnerability first disclosed.
  2. 11-08-2026
    Last modifiedVulnerability information updated.

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

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.28%

Chance of exploitation in the next 30 days

Percentile

21%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.28% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu89 products
  • linux< 5.15.0-37.39
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 5.15.0-1011.14
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 430a67f9d6169a7b3e328bceb2ef9542e4153c7c, < 65d8a737452e88f251fe5d925371de6d606df613 | ≥ 430a67f9d6169a7b3e328bceb2ef9542e4153c7c, < abc2129e646af7b43025d90a071f83043f1ae76c | ≥ 430a67f9d6169a7b3e328bceb2ef9542e4153c7c, < 4083925bd6dc89216d156474a8076feec904e607 | ≥ 430a67f9d6169a7b3e328bceb2ef9542e4153c7c, < 15729ff8143f8135b03988a100a19e66d7cb7ecd | 5.13
  • linux_kernel< 4.19.238 | ≥ 4.20, < 5.4.189 | ≥ 5.5, < 5.10.110 | ≥ 5.11, < 5.15.33 | ≥ 5.16, < 5.16.19 | ≥ 5.17, < 5.17.2
Debian1 product
  • linux< 5.17.3-1

3 vendors · 92 products

References

11 links
Show all 11 references