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CVE-2021-28688

Status: ModifiedMedium (6.5)—

The fix for XSA-365 includes initialization of pointers such that subsequent cleanup code wouldn't use uninitialized or stale values. This initialization went too far and may under certain conditions also overwrite pointers which are in need of cleaning up. The lack of cleanup would result in leaking persistent grants. The leak in turn would prevent fully cleaning up after a respective guest has died, leaving around zombie domains. All Linux versions having the fix for XSA-365 applied are vulnerable. XSA-365 was classified to affect versions back to at least 3.11.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (2)

Debian — Debian LinuxLinux — Linux Kernel

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-28688",
  "cveTags": [],
  "metrics": {
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          "baseScore": 2.1,
          "accessVector": "LOCAL",
          "vectorString": "AV:L/AC:L/Au:N/C:N/I:N/A:P",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "LOW",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 3.9,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
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          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 6.5,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
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        "impactScore": 4,
        "exploitabilityScore": 2
      }
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  "affected": [
    {
      "source": "security@xen.org",
      "affectedData": [
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          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "unknown",
              "version": "unspecified",
              "lessThan": "4.12",
              "versionType": "custom"
            },
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              "status": "affected",
              "version": "3.11",
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              "versionType": "custom"
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              "version": "next of 4.3",
              "lessThan": "unspecified",
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          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.12-rc"
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          "vendor": "Linux",
          "product": "Linux",
          "versions": [
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              "version": "5.10.18"
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        {
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
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              "status": "unknown",
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  ],
  "published": "2021-04-06T19:15:14.863",
  "references": [
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/06/msg00019.html",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@xen.org"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/06/msg00020.html",
      "tags": [
        "Third Party Advisory"
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      "source": "security@xen.org"
    },
    {
      "url": "https://xenbits.xenproject.org/xsa/advisory-371.txt",
      "tags": [
        "Patch",
        "Third Party Advisory"
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      "source": "security@xen.org"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/06/msg00019.html",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/06/msg00020.html",
      "tags": [
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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        "Third Party Advisory"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-665"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "The fix for XSA-365 includes initialization of pointers such that subsequent cleanup code wouldn't use uninitialized or stale values. This initialization went too far and may under certain conditions also overwrite pointers which are in need of cleaning up. The lack of cleanup would result in leaking persistent grants. The leak in turn would prevent fully cleaning up after a respective guest has died, leaving around zombie domains. All Linux versions having the fix for XSA-365 applied are vulnerable. XSA-365 was classified to affect versions back to at least 3.11."
    },
    {
      "lang": "es",
      "value": "La solución para XSA-365 incluye la inicialización de punteros de modo que el código de limpieza posterior no utilice valores no inicializados o obsoletos. Esta inicialización fue demasiado lejos y, en determinadas condiciones, también puede sobrescribir los punteros que están requiriendo una limpieza. La falta de limpieza resultaría en fugas de subsidios persistentes. A su vez, la filtración impediría a una limpieza completa después de que un invitado respectivo haya terminado, dejando dominios zombies. Todas las versiones de Linux que presentan la corrección para XSA-365 aplicada son vulnerables. XSA-365 se clasificó para afectar a las versiones de al menos 3.11"
    }
  ],
  "lastModified": "2026-06-17T03:46:47.920",
  "configurations": [
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      "nodes": [
        {
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}