{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2025-21920",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2025-21920",
    "idYear": 2025,
    "status": "PUBLISHED",
    "publishedAt": "2025-04-01T15:40:54.595Z",
    "updatedAt": "2026-05-11T21:09:05.513Z",
    "importedAt": "2026-10-24T01:57:29.455Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "vlan: enforce underlying device type",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nvlan: enforce underlying device type\n\nCurrently, VLAN devices can be created on top of non-ethernet devices.\n\nBesides the fact that it doesn't make much sense, this also causes a\nbug which leaks the address of a kernel function to usermode.\n\nWhen creating a VLAN device, we initialize GARP (garp_init_applicant)\nand MRP (mrp_init_applicant) for the underlying device.\n\nAs part of the initialization process, we add the multicast address of\neach applicant to the underlying device, by calling dev_mc_add.\n\n__dev_mc_add uses dev->addr_len to determine the length of the new\nmulticast address.\n\nThis causes an out-of-bounds read if dev->addr_len is greater than 6,\nsince the multicast addresses provided by GARP and MRP are only 6\nbytes long.\n\nThis behaviour can be reproduced using the following commands:\n\nip tunnel add gretest mode ip6gre local ::1 remote ::2 dev lo\nip l set up dev gretest\nip link add link gretest name vlantest type vlan id 100\n\nThen, the following command will display the address of garp_pdu_rcv:\n\nip maddr show | grep 01:80:c2:00:00:21\n\nFix the bug by enforcing the type of the underlying device during VLAN\ndevice initialization.",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "7f1564b2b2072b7aa1ac75350e9560a07c7a44fd"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "fa40ebef69234e39ec2d26930d045f2fb9a8cb2b"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "0fb7aa04c19eac4417f360a9f7611a60637bdacc"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "5a515d13e15536e82c5c7c83eb6cf5bc4827fee5"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "3561442599804905c3defca241787cd4546e99a7"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "30e8aee77899173a82ae5ed89f536c096f20aaeb"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "b6c72479748b7ea09f53ed64b223cee6463dc278"
            },
            {
              "version": "22bedad3ce112d5ca1eaf043d4990fa2ed698c87",
              "status": "affected",
              "versionType": "git",
              "lessThan": "b33a534610067ade2bdaf2052900aaad99701353"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "2.6.35",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "2.6.35"
            },
            {
              "version": "5.4.291",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.4.*"
            },
            {
              "version": "5.10.235",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "version": "5.15.179",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "version": "6.1.131",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "version": "6.6.83",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "version": "6.12.19",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "version": "6.13.7",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.13.*"
            },
            {
              "version": "6.14",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}