{
  "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-2024-49940",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2024-49940",
    "idYear": 2024,
    "status": "PUBLISHED",
    "publishedAt": "2024-10-21T18:01:59.668Z",
    "updatedAt": "2026-10-21T12:35:24.401Z",
    "importedAt": "2026-10-24T01:57:16.009Z",
    "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": "l2tp: prevent possible tunnel refcount underflow",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: prevent possible tunnel refcount underflow\n\nWhen a session is created, it sets a backpointer to its tunnel. When\nthe session refcount drops to 0, l2tp_session_free drops the tunnel\nrefcount if session->tunnel is non-NULL. However, session->tunnel is\nset in l2tp_session_create, before the tunnel refcount is incremented\nby l2tp_session_register, which leaves a small window where\nsession->tunnel is non-NULL when the tunnel refcount hasn't been\nbumped.\n\nMoving the assignment to l2tp_session_register is trivial but\nl2tp_session_create calls l2tp_session_set_header_len which uses\nsession->tunnel to get the tunnel's encap. Add an encap arg to\nl2tp_session_set_header_len to avoid using session->tunnel.\n\nIf l2tpv3 sessions have colliding IDs, it is possible for\nl2tp_v3_session_get to race with l2tp_session_register and fetch a\nsession which doesn't yet have session->tunnel set. Add a check for\nthis case.",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
              "status": "affected",
              "versionType": "git",
              "lessThan": "98691b2e28a6c3dac0680914493d54c77f215755"
            },
            {
              "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
              "status": "affected",
              "versionType": "git",
              "lessThan": "f7415e60c25a6108cd7955a20b2e66b6251ffe02"
            },
            {
              "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
              "status": "affected",
              "versionType": "git",
              "lessThan": "24256415d18695b46da06c93135f5b51c548b950"
            },
            {
              "version": "b102bfc2a90d14f342580285782a9a51c74f7369",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "10c15ddabbcf888922adbdd44ca3fecf6eab19d9",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "8d1c650d452c53fcb3f02a7b1d772741639f89a4",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "12b5fb58ac993c24210cf8cbc72d407d3a4e6490",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "aef37401b467a0b1a9517c69924a1d66937e0789",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "3.2.99",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "3.3"
            },
            {
              "version": "3.16.54",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "3.17"
            },
            {
              "version": "4.4.225",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.5"
            },
            {
              "version": "4.9.225",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.10"
            },
            {
              "version": "4.14.182",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.15"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "4.15",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "4.15"
            },
            {
              "version": "6.6.160",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "version": "6.11.3",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.11.*"
            },
            {
              "version": "6.12",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}