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CVE-2021-47107 (GCVE-0-2021-47107)

Vulnerability from cvelistv5 – Published: 2024-03-04 18:15 – Updated: 2026-08-05 08:46
VLAI
Title
NFSD: Fix READDIR buffer overflow
Summary
In the Linux kernel, the following vulnerability has been resolved: NFSD: Fix READDIR buffer overflow If a client sends a READDIR count argument that is too small (say, zero), then the buffer size calculation in the new init_dirlist helper functions results in an underflow, allowing the XDR stream functions to write beyond the actual buffer. This calculation has always been suspect. NFSD has never sanity- checked the READDIR count argument, but the old entry encoders managed the problem correctly. With the commits below, entry encoding changed, exposing the underflow to the pointer arithmetic in xdr_reserve_space(). Modern NFS clients attempt to retrieve as much data as possible for each READDIR request. Also, we have no unit tests that exercise the behavior of READDIR at the lower bound of @count values. Thus this case was missed during testing.
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: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-07-24 14:23 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 37aa5e64022243e721b8334122997881177a4cfc , < 9e291a6a28d32545ed2fd959a8165144d1724df1 (git)
Affected: 7f87fc2d34d475225e78b7f5c4eabb121f4282b2 , < eabc0aab98e5218ceecd82069b0d6fdfff5ee885 (git)
Affected: 7f87fc2d34d475225e78b7f5c4eabb121f4282b2 , < 53b1119a6e5028b125f431a0116ba73510d82a72 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.13
Unaffected: 0 , < 5.13 (semver)
Unaffected: 5.15.12 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
guessed Create a notification for this product.
Show details on NVD website
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Este c\u00e1lculo siempre ha sido sospechoso. NFSD nunca ha verificado la cordura del argumento de conteo READDIR, pero los codificadores de entrada antiguos manejaron el problema correctamente. Con las confirmaciones a continuaci\u00f3n, la codificaci\u00f3n de entrada cambi\u00f3, exponiendo el desbordamiento a la aritm\u00e9tica del puntero en xdr_reserve_space(). Los clientes NFS modernos intentan recuperar la mayor cantidad de datos posible para cada solicitud READDIR. Adem\u00e1s, no tenemos pruebas unitarias que ejerzan el comportamiento de READDIR en el l\u00edmite inferior de los valores @count. 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    "redhat_vex": {
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      "current_release_date": "2026-08-04T20:05:38+00:00",
      "cve": "CVE-2021-47107",
      "id": "CVE-2021-47107",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:fixed": "120",
      "product_status:known_affected": "58",
      "product_status:known_not_affected": "108",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: NFSD: Fix READDIR buffer overflow",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47107.json",
      "version": "3"
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    "suse_vex": {
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      "current_release_date": "2026-09-05T17:10:52Z",
      "cve": "CVE-2021-47107",
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      "product_status:known_affected": "260",
      "product_status:known_not_affected": "264",
      "product_status:recommended": "491",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-47107",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-47107.json",
      "version": "58"
    },
    "vulnrichment": {
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NFSD has never sanity-\\nchecked the READDIR count argument, but the old entry encoders\\nmanaged the problem correctly.\\n\\nWith the commits below, entry encoding changed, exposing the\\nunderflow to the pointer arithmetic in xdr_reserve_space().\\n\\nModern NFS clients attempt to retrieve as much data as possible\\nfor each READDIR request. Also, we have no unit tests that\\nexercise the behavior of READDIR at the lower bound of @count\\nvalues. Thus this case was missed during testing.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.12\", \"versionStartIncluding\": \"5.13\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16\", \"versionStartIncluding\": \"5.13\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T08:46:02.458Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47107\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:46:02.458Z\", \"dateReserved\": \"2024-03-04T18:12:48.835Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-03-04T18:15:38.706Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.