Vulnerability-Lookup

GHSA-8QGG-VJ9J-HH4R

Vulnerability from github – Published: 2025-02-27 18:31 – Updated: 2025-02-27 18:31

Details

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

Severity

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2021-47646"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-02-26T06:37:06Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\n\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already-setup queue merges\"). The\nlatter was then reverted by commit ebc69e897e17 (\"Revert \"block, bfq:\nhonor already-setup queue merges\"\"). Yet, the reverted commit was not\nthe one introducing the bug. In fact, it actually triggered a UAF\nintroduced by a different commit, and now fixed by commit d29bd41428cf\n(\"block, bfq: reset last_bfqq_created on group change\").\n\nSo, there is no point in keeping commit 2d52c58b9c9b (\"block, bfq:\nhonor already-setup queue merges\") out. This commit restores it.\n\n[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503",
  "id": "GHSA-8qgg-vj9j-hh4r",
  "modified": "2025-02-27T18:31:07Z",
  "published": "2025-02-27T18:31:07Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47646"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/931aff627469a75c77b9fd3823146d0575afffd6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cc051f497eac9d8a0d816cd4bffa3415f2724871"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f990f0985eda59d4f29fc83fcf300c92b1225d39"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2021-47646 (GCVE-0-2021-47646)

Vulnerability from cvelistv5 – Published: 2025-02-26 01:54 – Updated: 2026-08-11 02:05

Title

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

Summary

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

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-02-27 17:59 UTC

CWE

CWE-416 - Use After Free

Assigner

Linux CNA under the mitre root

CNA scorecard D 54/100 over 6618 records in the last 180 days details

References

4 references

URL	Tags
https://git.kernel.org/stable/c/65d8a737452e88f25…
https://git.kernel.org/stable/c/abc2129e646af7b43…
https://git.kernel.org/stable/c/4083925bd6dc89216…
https://git.kernel.org/stable/c/15729ff8143f8135b…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 430a67f9d6169a7b3e328bceb2ef9542e4153c7c , < 65d8a737452e88f251fe5d925371de6d606df613 (git) Affected: 430a67f9d6169a7b3e328bceb2ef9542e4153c7c , < abc2129e646af7b43025d90a071f83043f1ae76c (git) Affected: 430a67f9d6169a7b3e328bceb2ef9542e4153c7c , < 4083925bd6dc89216d156474a8076feec904e607 (git) Affected: 430a67f9d6169a7b3e328bceb2ef9542e4153c7c , < 15729ff8143f8135b03988a100a19e66d7cb7ecd (git)
Linux	Linux	Affected: 5.13 Unaffected: 0 , < 5.13 (semver) Unaffected: 5.15.33 , ≤ 5.15.* (semver) Unaffected: 5.16.19 , ≤ 5.16.* (semver) Unaffected: 5.17.2 , ≤ 5.17.* (semver) Unaffected: 5.18 , ≤ * (original_commit_for_fix)

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "LOCAL",
              "availabilityImpact": "HIGH",
              "baseScore": 7.8,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "LOW",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2021-47646",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-02-27T17:59:39.194997Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-416",
                "description": "CWE-416 Use After Free",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-02-27T18:02:30.637Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "block/bfq-iosched.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "65d8a737452e88f251fe5d925371de6d606df613",
              "status": "affected",
              "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c",
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            },
            {
              "lessThan": "abc2129e646af7b43025d90a071f83043f1ae76c",
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            {
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              "status": "affected",
              "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c",
              "versionType": "git"
            },
            {
              "lessThan": "15729ff8143f8135b03988a100a19e66d7cb7ecd",
              "status": "affected",
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        },
        {
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.13"
            },
            {
              "lessThan": "5.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.33",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.16.*",
              "status": "unaffected",
              "version": "5.16.19",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.17.*",
              "status": "unaffected",
              "version": "5.17.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "5.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.33",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                {
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                {
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              "negate": false,
              "operator": "OR"
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      ],
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\n\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already-setup queue merges\"). The\nlatter was then reverted by commit ebc69e897e17 (\"Revert \"block, bfq:\nhonor already-setup queue merges\"\"). Yet, the reverted commit was not\nthe one introducing the bug. In fact, it actually triggered a UAF\nintroduced by a different commit, and now fixed by commit d29bd41428cf\n(\"block, bfq: reset last_bfqq_created on group change\").\n\nSo, there is no point in keeping commit 2d52c58b9c9b (\"block, bfq:\nhonor already-setup queue merges\") out. This commit restores it.\n\n[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503"
        }
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      "metrics": [
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            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerability is in the BFQ block I/O scheduler and is reached via local syscalls that submit I/O (read/write/fsync/ioctl), through bfq_init_rq \u2192 bfq_get_queue / bfq_setup_cooperator; it is not reachable from network packet processing.\nAC:L - An unprivileged attacker can reliably drive the buggy path by spawning processes that issue concurrent I/O and by migrating between blkcgs so queues are created, merged, moved, and freed under attacker control; success does not depend on victim state beyond BFQ being the active scheduler.\nPR:L - Only an unprivileged local account is required to submit I/O on a BFQ-scheduled device; changing the elevator needs privileges, but BFQ (with group I/O scheduling) is a common/default deployment (e.g. Android), so the attacker need not already be root.\nUI:N - Exploitation requires no action by another user; the attacker triggers the bug solely through their own I/O and process/cgroup activity.\nS:U - Impact is confined to the local kernel\u0027s security authority (memory corruption / privilege escalation on the host); there is no VM escape, IOMMU bypass, or other cross-boundary scope change.\nC:H - The issue is a use-after-free of bfq_queue objects (dangling last_bfqq_created / broken merge state), which per kernel CVSS guidance yields an arbitrary-read primitive via heap reuse of the freed object.\nI:H - The same UAF/memory-corruption condition enables heap spraying and arbitrary-write / control-flow hijacking in kernel context, so integrity impact is High.\nA:H - The bug causes kernel oops/BUG_ON and slab freelist corruption (demonstrated in bugzilla 214503 crashes in bfq_get_queue / bfq_do_early_stable_merge), so availability impact is High."
            }
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        }
      ],
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        "dateUpdated": "2026-08-11T02:05:32.009Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        {
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      ],
      "title": "Revert \"Revert \"block, bfq: honor already-setup queue merges\"\"",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2021-47646",
    "datePublished": "2025-02-26T01:54:15.122Z",
    "dateReserved": "2025-02-26T01:48:21.520Z",
    "dateUpdated": "2026-08-11T02:05:32.009Z",
    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-8QGG-VJ9J-HH4R

CVE-2021-47646 (GCVE-0-2021-47646)

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Sightings

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Related by attack behaviour