CVE-2021-47646

Estado: ModificadaAlta (7.8)—

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.

Leer descripción completaMostrar menos

[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.28%
Percentil entre todas las CVEs puntuadas: 19
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Impacto principalT1059 Command and Scripting Interpreterexecution75 %

CWE-416 (Use-After-Free) con AV:L/PR:L permite escalada de privilegios local; subsistema block/bfq del kernel Linux. La pista sugiere T1068/T1059, coherente con UAF que puede permitir ejecución de código con privilegios elevados.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Execution Prevention Threat Intelligence Program Restrict Web-Based Content Privileged Account Management Limit Software Installation Behavior Prevention on Endpoint

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416

Referencias

JSON original (NVD)

Mostrar

{
  "id": "CVE-2021-47646",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-47646",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2025-02-27T17:59:39.194997Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      },
      {
        "type": "Secondary",
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c",
              "lessThan": "65d8a737452e88f251fe5d925371de6d606df613",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c",
              "lessThan": "abc2129e646af7b43025d90a071f83043f1ae76c",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c",
              "lessThan": "4083925bd6dc89216d156474a8076feec904e607",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c",
              "lessThan": "15729ff8143f8135b03988a100a19e66d7cb7ecd",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "block/bfq-iosched.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.13"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "5.13",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.15.33",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "status": "unaffected",
              "version": "5.16.19",
              "versionType": "semver",
              "lessThanOrEqual": "5.16.*"
            },
            {
              "status": "unaffected",
              "version": "5.17.2",
              "versionType": "semver",
              "lessThanOrEqual": "5.17.*"
            },
            {
              "status": "unaffected",
              "version": "5.18",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "block/bfq-iosched.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2025-02-26T06:37:06.390",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "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"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: Revert \"Revert \"block, bfq: respetar las fusiones de colas ya configuradas\"\" Se produjo un fallo [1] junto con la confirmación 2d52c58b9c9b (\"block, bfq: respetar las fusiones de colas ya configuradas\"). Esta última se revirtió mediante la confirmación ebc69e897e17 (\"Revert \"block, bfq: respetar las fusiones de colas ya configuradas\"\"). Sin embargo, la confirmación revertida no fue la que introdujo el error. De hecho, activó una UAF introducida por una confirmación diferente, y ahora corregida por la confirmación d29bd41428cf (\"block, bfq: restablecer last_bfqq_created al cambiar de grupo\"). Por lo tanto, no tiene sentido mantener la confirmación 2d52c58b9c9b (\"block, bfq: respetar las fusiones de colas ya configuradas\"). Esta confirmación la restaura. [1] https://bugzilla.kernel.org/show_bug.cgi?id=214503"
    }
  ],
  "lastModified": "2026-08-11T03:17:33.693",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E0B62342-F287-4C6B-92AA-C1BC61DDAFFA",
              "versionEndExcluding": "4.19.238"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "8CB6E8F5-C2B1-46F3-A807-0F6104AC340F",
              "versionEndExcluding": "5.4.189",
              "versionStartIncluding": "4.20"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "91D3BFD0-D3F3-4018-957C-96CCBF357D79",
              "versionEndExcluding": "5.10.110",
              "versionStartIncluding": "5.5"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "27C42AE8-B387-43E2-938A-E1C8B40BE6D5",
              "versionEndExcluding": "5.15.33",
              "versionStartIncluding": "5.11"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "20C43679-0439-405A-B97F-685BEE50613B",
              "versionEndExcluding": "5.16.19",
              "versionStartIncluding": "5.16"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "210C679C-CF84-44A3-8939-E629C87E54BF",
              "versionEndExcluding": "5.17.2",
              "versionStartIncluding": "5.17"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}