Vulnerability-Lookup

FKIE_CVE-2021-47506

Vulnerability from fkie_nvd - Published: 2024-05-24 15:15 - Updated: 2026-08-04 10:17

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease. A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebce	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536ee	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebce	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536ee	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/548ec0805c399c65ed66c6641be467f717833ab5	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/e0759696de6851d7536efddfdd2dfed4c4df1f09	Patch
af854a3a-2127-422b-91ae-364da2661108	https://git.kernel.org/stable/c/eeb0711801f5e19ef654371b627682aed3b11373	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	5.15
linux	linux_kernel	5.15
linux	linux_kernel	5.15
linux	linux_kernel	5.15

JSON

To clipboard

{
  "affected": [
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      "affectedData": [
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          "programFiles": [
            "fs/nfsd/nfs4state.c"
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          "vendor": "Linux",
          "versions": [
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            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "4.9.294",
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            {
              "lessThanOrEqual": "4.14.*",
              "status": "unaffected",
              "version": "4.14.259",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "4.19.*",
              "status": "unaffected",
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              "version": "5.4.168",
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              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.85",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "5.16",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix use-after-free due to delegation race\n\nA delegation break could arrive as soon as we\u0027ve called vfs_setlease.  A\ndelegation break runs a callback which immediately (in\nnfsd4_cb_recall_prepare) adds the delegation to del_recall_lru.  If we\nthen exit nfs4_set_delegation without hashing the delegation, it will be\nfreed as soon as the callback is done with it, without ever being\nremoved from del_recall_lru.\n\nSymptoms show up later as use-after-free or list corruption warnings,\nusually in the laundromat thread.\n\nI suspect aba2072f4523 \"nfsd: grant read delegations to clients holding\nwrites\" made this bug easier to hit, but I looked as far back as v3.0\nand it looks to me it already had the same problem.  So I\u0027m not sure\nwhere the bug was introduced; it may have been there from the beginning."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: nfsd: corrige el use-after-free debido a la ejecuci\u00f3n de delegaci\u00f3n. Una interrupci\u00f3n de la delegaci\u00f3n podr\u00eda llegar tan pronto como hayamos llamado a vfs_setlease. Una interrupci\u00f3n de la delegaci\u00f3n ejecuta una devoluci\u00f3n de llamada que inmediatamente (en nfsd4_cb_recall_prepare) agrega la delegaci\u00f3n a del_recall_lru. Si luego salimos de nfs4_set_delegation sin aplicar hash a la delegaci\u00f3n, se liberar\u00e1 tan pronto como finalice la devoluci\u00f3n de llamada, sin eliminarse nunca de del_recall_lru. Los s\u00edntomas aparecen m\u00e1s tarde como advertencias de use-after-free o de corrupci\u00f3n en la lista, generalmente en el hilo de la lavander\u00eda. Sospecho que aba2072f4523 \"nfsd: otorgar delegaciones de lectura a clientes que tienen escrituras\" hizo que este error fuera m\u00e1s f\u00e1cil de corregir, pero mir\u00e9 hasta la versi\u00f3n 3.0 y me parece que ya ten\u00eda el mismo problema. Entonces no estoy seguro de d\u00f3nde se introdujo el error; puede que haya estado ah\u00ed desde el principio."
    }
  ],
  "id": "CVE-2021-47506",
  "lastModified": "2026-08-04T10:17:06.590",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "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"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-47506",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2024-05-29T17:04:47.932390Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2024-05-24T15:15:11.197",
  "references": [
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  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
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      "source": "nvd@nist.gov",
      "type": "Primary"
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}

CVE-2021-47506 (GCVE-0-2021-47506)

Vulnerability from cvelistv5 – Published: 2024-05-24 15:01 – Updated: 2026-08-05 08:48

Title

nfsd: fix use-after-free due to delegation race

Summary

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/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 2024-05-29 17:04 UTC

Assigner

Linux mitre root

References

8 references

URL	Tags
https://git.kernel.org/stable/c/04a8d07f3d58308b9…
https://git.kernel.org/stable/c/348714018139c3953…
https://git.kernel.org/stable/c/33645d3e22720cac1…
https://git.kernel.org/stable/c/2becaa990b93cbd29…
https://git.kernel.org/stable/c/e0759696de6851d75…
https://git.kernel.org/stable/c/eeb0711801f5e19ef…
https://git.kernel.org/stable/c/148c816f10fd11df2…
https://git.kernel.org/stable/c/548ec0805c399c65e…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < 04a8d07f3d58308b92630045560799a3faa3ebce (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < 348714018139c39533c55661a0c7c990671396b4 (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < 33645d3e22720cac1e4548f8fef57bf0649536ee (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < 2becaa990b93cbd2928292c0b669d3abb6cf06d4 (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < e0759696de6851d7536efddfdd2dfed4c4df1f09 (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < eeb0711801f5e19ef654371b627682aed3b11373 (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < 148c816f10fd11df27ca6a9b3238cdd42fa72cd3 (git) Affected: dff1399f8addf7129c49bb2227469da79cc30b47 , < 548ec0805c399c65ed66c6641be467f717833ab5 (git)
Linux	Linux	Affected: 3.17 Unaffected: 0 , < 3.17 (semver) Unaffected: 4.4.296 , ≤ 4.4.* (semver) Unaffected: 4.9.294 , ≤ 4.9.* (semver) Unaffected: 4.14.259 , ≤ 4.14.* (semver) Unaffected: 4.19.222 , ≤ 4.19.* (semver) Unaffected: 5.4.168 , ≤ 5.4.* (semver) Unaffected: 5.10.85 , ≤ 5.10.* (semver) Unaffected: 5.15.8 , ≤ 5.15.* (semver) Unaffected: 5.16 , ≤ * (original_commit_for_fix)

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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.

Detection rules are retrieved from Rulezet.

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.