ubuntu-cve-2021-3996
Vulnerability from osv_ubuntu
Published
2022-02-01 00:00
Modified
2026-04-22 07:39
Summary
Details

A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows a local user on a vulnerable system to unmount other users' filesystems that are either world-writable themselves (like /tmp) or mounted in a world-writable directory. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "bsdutils",
            "binary_version": "1:2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "fdisk",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "libblkid1",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "libfdisk1",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "libmount1",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "libsmartcols1",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "libuuid1",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "mount",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "rfkill",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "util-linux",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "util-linux-locales",
            "binary_version": "2.34-0.1ubuntu9.3"
          },
          {
            "binary_name": "uuid-runtime",
            "binary_version": "2.34-0.1ubuntu9.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "util-linux",
        "purl": "pkg:deb/ubuntu/util-linux@2.34-0.1ubuntu9.3?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.34-0.1ubuntu9.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.34-0.1ubuntu2",
        "2.34-0.1ubuntu4",
        "2.34-0.1ubuntu5",
        "2.34-0.1ubuntu6",
        "2.34-0.1ubuntu7",
        "2.34-0.1ubuntu8",
        "2.34-0.1ubuntu9",
        "2.34-0.1ubuntu9.1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "bsdextrautils",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "bsdutils",
            "binary_version": "1:2.37.2-4ubuntu2"
          },
          {
            "binary_name": "eject",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "fdisk",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "libblkid1",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "libfdisk1",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "libmount1",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "libsmartcols1",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "libuuid1",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "mount",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "rfkill",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "util-linux",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "util-linux-locales",
            "binary_version": "2.37.2-4ubuntu2"
          },
          {
            "binary_name": "uuid-runtime",
            "binary_version": "2.37.2-4ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "util-linux",
        "purl": "pkg:deb/ubuntu/util-linux@2.37.2-4ubuntu2?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.37.2-4ubuntu2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.36.1-8ubuntu1",
        "2.37.2-4ubuntu1"
      ]
    }
  ],
  "aliases": [],
  "details": "A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows a local user on a vulnerable system to unmount other users\u0027 filesystems that are either world-writable themselves (like /tmp) or mounted in a world-writable directory. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.",
  "id": "UBUNTU-CVE-2021-3996",
  "modified": "2026-04-22T07:39:50Z",
  "published": "2022-02-01T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-3996"
    },
    {
      "type": "REPORT",
      "url": "https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotes"
    },
    {
      "type": "REPORT",
      "url": "https://www.openwall.com/lists/oss-security/2022/01/24/2"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-5279-1"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2021-3996"
    }
  ],
  "related": [
    "USN-5279-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2021-3996"
  ]
}



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