Security advisory

{
  "id": "13cef32ad889196ec6c7c9ea7946f702b4a489dffd19dfecced0be5b025294b5",
  "url": "https://osv.dev/vulnerability/CVE-2021-3995",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-3995",
    "summary": "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 an unprivileged local attacker to unmount FUSE filesystems that belong to certain other users who have a UID that is a prefix of the UID of the attacker in its string form. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.",
    "evidence": "osv:CVE-2021-3995",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2021-3995",
      "aliases": [
        "CVE-2021-3995"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/util-linux/util-linux",
              "type": "GIT",
              "events": [
                {
                  "introduced": "d4319b91c9d7d69e7b954fc66819214f81501312"
                },
                {
                  "fixed": "331a1e6e10f7943a12112c7161a8c995c1c5b9b9"
                },
                {
                  "fixed": "57202f5713afa2af20ffbb6ab5331481d0396f8d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:kernel:util-linux:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.34"
                      },
                      {
                        "fixed": "2.37.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "57202f5713afa2af20ffbb6ab5331481d0396f8d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.37.2",
            "v2.37.1",
            "v2.37",
            "v2.37-rc2",
            "v2.37-rc1",
            "v2.36",
            "v2.36-rc2",
            "v2.36-rc1",
            "v2.35",
            "v2.35-rc2",
            "v2.35-rc1",
            "v2.34"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-3995.json",
            "vanir_signatures": [
              {
                "id": "CVE-2021-3995-1269fc08",
                "digest": {
                  "threshold": 0.9,
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                },
                "source": "https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d",
                "target": {
                  "file": "libmount/src/context_umount.c"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              },
              {
                "id": "CVE-2021-3995-2ca3bb48",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
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                },
                "source": "https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d",
                "target": {
                  "file": "libmount/src/mountP.h"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              },
              {
                "id": "CVE-2021-3995-74f6c434",
                "digest": {
                  "length": 908,
                  "function_hash": "109824080416446340833412381312032531836"
                },
                "source": "https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d",
                "target": {
                  "file": "libmount/src/context_umount.c",
                  "function": "is_fuse_usermount"
                },
                "deprecated": false,
                "signature_type": "Function",
                "signature_version": "v1"
              },
              {
                "id": "CVE-2021-3995-a6de3fc7",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
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                },
                "source": "https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d",
                "target": {
                  "file": "libmount/src/optstr.c"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
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            ],
            "vanir_signatures_modified": "2026-10-20T14:08:46Z"
          }
        }
      ],
      "modified": "2026-10-20T14:08:46.309599271Z",
      "provider": "osv",
      "references": [
        "https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotes",
        "https://security.gentoo.org/glsa/202401-08",
        "https://security.netapp.com/advisory/ntap-20221209-0002/",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2024631https://access.redhat.com/security/cve/CVE-2021-3995",
        "https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d",
        "https://www.openwall.com/lists/oss-security/2022/01/24/2"
      ],
      "provider_metadata": {
        "unresolved_ranges": [
          {
            "cpes": [
              "cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*"
            ],
            "vendor_product": "fedoraproject:fedora",
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "35"
                  },
                  {
                    "last_affected": "35"
                  }
                ],
                "source": "CPE_STRING"
              }
            ]
          }
        ]
      }
    },
    "related_cves": [
      {
        "value": "CVE-2021-3995",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 388572,
  "published_at": "2022-08-23T20:15:08.493+00:00"
}