FKIE_CVE-2021-3493

Vulnerability from fkie_nvd - Published: 2021-04-17 05:15 - Updated: 2025-10-28 13:49
Severity ?
8.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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
The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.
References
security@ubuntu.comhttp://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.htmlExploit, Third Party Advisory, VDB Entry
security@ubuntu.comhttp://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.htmlThird Party Advisory, VDB Entry, Press/Media Coverage
security@ubuntu.comhttp://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.htmlExploit, Third Party Advisory, VDB Entry
security@ubuntu.comhttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52Mailing List, Patch, Third Party Advisory
security@ubuntu.comhttps://ubuntu.com/security/notices/USN-4917-1Vendor Advisory
security@ubuntu.comhttps://www.openwall.com/lists/oss-security/2021/04/16/1Mailing List, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.htmlExploit, Third Party Advisory, VDB Entry
af854a3a-2127-422b-91ae-364da2661108http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.htmlThird Party Advisory, VDB Entry, Press/Media Coverage
af854a3a-2127-422b-91ae-364da2661108http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.htmlExploit, Third Party Advisory, VDB Entry
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52Mailing List, Patch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://ubuntu.com/security/notices/USN-4917-1Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108https://www.openwall.com/lists/oss-security/2021/04/16/1Mailing List, Third Party Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493US Government Resource
Impacted products
Vendor Product Version
canonical ubuntu_linux *
canonical ubuntu_linux *
canonical ubuntu_linux *
To clipboard 

{
  "cisaActionDue": "2022-11-10",
  "cisaExploitAdd": "2022-10-20",
  "cisaRequiredAction": "Apply updates per vendor instructions.",
  "cisaVulnerabilityName": "Linux Kernel Privilege Escalation Vulnerability",
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:canonical:ubuntu_linux:*:*:*:*:lts:*:*:*",
              "matchCriteriaId": "90A80DE7-3EFA-464C-9D31-C46521FFBFBF",
              "versionEndExcluding": "18.04",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:canonical:ubuntu_linux:*:*:*:*:lts:*:*:*",
              "matchCriteriaId": "2027773B-26DA-408E-B71D-40D05690D9EA",
              "versionEndExcluding": "20.04",
              "versionStartIncluding": "18.04.1",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:canonical:ubuntu_linux:*:*:*:*:-:*:*:*",
              "matchCriteriaId": "ACAB2EE0-EC21-4669-840F-94F6C3028C64",
              "versionEndExcluding": "20.10",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges."
    },
    {
      "lang": "es",
      "value": "La implementaci\u00f3n de overlayfs en el kernel de Linux no comprob\u00f3 apropiadamente con respecto a los espacios de nombre de los usuarios, la configuraci\u00f3n de las capacidades de los archivos en un sistema de archivos subyacente.\u0026#xa0;Debido a la combinaci\u00f3n de los espacios de nombre de usuarios no privilegiados junto con un parche incluido en el kernel de Ubuntu para permitir montajes de superposici\u00f3n no privilegiados, un atacante podr\u00eda usar esto para alcanzar privilegios elevados"
    }
  ],
  "id": "CVE-2021-3493",
  "lastModified": "2025-10-28T13:49:50.883",
  "metrics": {
    "cvssMetricV2": [
      {
        "acInsufInfo": false,
        "baseSeverity": "HIGH",
        "cvssData": {
          "accessComplexity": "LOW",
          "accessVector": "LOCAL",
          "authentication": "NONE",
          "availabilityImpact": "COMPLETE",
          "baseScore": 7.2,
          "confidentialityImpact": "COMPLETE",
          "integrityImpact": "COMPLETE",
          "vectorString": "AV:L/AC:L/Au:N/C:C/I:C/A:C",
          "version": "2.0"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 10.0,
        "obtainAllPrivilege": false,
        "obtainOtherPrivilege": false,
        "obtainUserPrivilege": false,
        "source": "nvd@nist.gov",
        "type": "Primary",
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.0,
        "impactScore": 6.0,
        "source": "security@ubuntu.com",
        "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"
      }
    ]
  },
  "published": "2021-04-17T05:15:14.630",
  "references": [
    {
      "source": "security@ubuntu.com",
      "tags": [
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        "Third Party Advisory",
        "VDB Entry"
      ],
      "url": "http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html"
    },
    {
      "source": "security@ubuntu.com",
      "tags": [
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        "VDB Entry",
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      "url": "http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html"
    },
    {
      "source": "security@ubuntu.com",
      "tags": [
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      ],
      "url": "http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html"
    },
    {
      "source": "security@ubuntu.com",
      "tags": [
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        "Third Party Advisory"
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      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52"
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    },
    {
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    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
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    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
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    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
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    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "US Government Resource"
      ],
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493"
    }
  ],
  "sourceIdentifier": "security@ubuntu.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-270"
        }
      ],
      "source": "security@ubuntu.com",
      "type": "Secondary"
    },
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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  • 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.
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Detection rules are retrieved from Rulezet.