FKIE_CVE-2024-49940

Vulnerability from fkie_nvd - Published: 2024-10-21 18:15 - Updated: 2026-06-17 08:00
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: l2tp: prevent possible tunnel refcount underflow When a session is created, it sets a backpointer to its tunnel. When the session refcount drops to 0, l2tp_session_free drops the tunnel refcount if session->tunnel is non-NULL. However, session->tunnel is set in l2tp_session_create, before the tunnel refcount is incremented by l2tp_session_register, which leaves a small window where session->tunnel is non-NULL when the tunnel refcount hasn't been bumped. Moving the assignment to l2tp_session_register is trivial but l2tp_session_create calls l2tp_session_set_header_len which uses session->tunnel to get the tunnel's encap. Add an encap arg to l2tp_session_set_header_len to avoid using session->tunnel. If l2tpv3 sessions have colliding IDs, it is possible for l2tp_v3_session_get to race with l2tp_session_register and fetch a session which doesn't yet have session->tunnel set. Add a check for this case.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/24256415d18695b46da06c93135f5b51c548b950Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f7415e60c25a6108cd7955a20b2e66b6251ffe02Patch
Impacted products
Vendor Product Version
linux linux_kernel *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/l2tp/l2tp_core.c",
            "net/l2tp/l2tp_core.h",
            "net/l2tp/l2tp_netlink.c",
            "net/l2tp/l2tp_ppp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f7415e60c25a6108cd7955a20b2e66b6251ffe02",
              "status": "affected",
              "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
              "versionType": "git"
            },
            {
              "lessThan": "24256415d18695b46da06c93135f5b51c548b950",
              "status": "affected",
              "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "b102bfc2a90d14f342580285782a9a51c74f7369",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "10c15ddabbcf888922adbdd44ca3fecf6eab19d9",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "8d1c650d452c53fcb3f02a7b1d772741639f89a4",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "12b5fb58ac993c24210cf8cbc72d407d3a4e6490",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "aef37401b467a0b1a9517c69924a1d66937e0789",
              "versionType": "git"
            },
            {
              "lessThan": "3.3",
              "status": "affected",
              "version": "3.2.99",
              "versionType": "semver"
            },
            {
              "lessThan": "3.17",
              "status": "affected",
              "version": "3.16.54",
              "versionType": "semver"
            },
            {
              "lessThan": "4.5",
              "status": "affected",
              "version": "4.4.225",
              "versionType": "semver"
            },
            {
              "lessThan": "4.10",
              "status": "affected",
              "version": "4.9.225",
              "versionType": "semver"
            },
            {
              "lessThan": "4.15",
              "status": "affected",
              "version": "4.14.182",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/l2tp/l2tp_core.c",
            "net/l2tp/l2tp_core.h",
            "net/l2tp/l2tp_netlink.c",
            "net/l2tp/l2tp_ppp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.15"
            },
            {
              "lessThan": "4.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.11.*",
              "status": "unaffected",
              "version": "6.11.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.12",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "6D5FF9C2-A011-4A64-B614-F9244ED2EA0D",
              "versionEndExcluding": "6.11.3",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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-\u003etunnel is non-NULL. However, session-\u003etunnel is\nset in l2tp_session_create, before the tunnel refcount is incremented\nby l2tp_session_register, which leaves a small window where\nsession-\u003etunnel is non-NULL when the tunnel refcount hasn\u0027t 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-\u003etunnel to get the tunnel\u0027s encap. Add an encap arg to\nl2tp_session_set_header_len to avoid using session-\u003etunnel.\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\u0027t yet have session-\u003etunnel set. Add a check for\nthis case."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: l2tp: evitar un posible desbordamiento del recuento de referencias del t\u00fanel Cuando se crea una sesi\u00f3n, establece un puntero hacia atr\u00e1s a su t\u00fanel. Cuando el recuento de referencias de la sesi\u00f3n cae a 0, l2tp_session_free descarta el recuento de referencias del t\u00fanel si session-\u0026gt;tunnel no es NULL. Sin embargo, session-\u0026gt;tunnel se establece en l2tp_session_create, antes de que el recuento de referencias del t\u00fanel se incremente mediante l2tp_session_register, lo que deja una peque\u00f1a ventana donde session-\u0026gt;tunnel no es NULL cuando el recuento de referencias del t\u00fanel no se ha incrementado. Mover la asignaci\u00f3n a l2tp_session_register es trivial, pero l2tp_session_create llama a l2tp_session_set_header_len, que usa session-\u0026gt;tunnel para obtener el encap del t\u00fanel. Agregue un argumento de encap a l2tp_session_set_header_len para evitar usar session-\u0026gt;tunnel. Si las sesiones l2tpv3 tienen identificadores en conflicto, es posible que l2tp_v3_session_get compita con l2tp_session_register y obtenga una sesi\u00f3n que a\u00fan no tenga configurado session-\u0026gt;tunnel. Agregue una verificaci\u00f3n para este caso."
    }
  ],
  "id": "CVE-2024-49940",
  "lastModified": "2026-06-17T08:00:46.797",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2024-49940",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2024-10-22T13:37:52.827630Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2024-10-21T18:15:15.703",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/24256415d18695b46da06c93135f5b51c548b950"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/f7415e60c25a6108cd7955a20b2e66b6251ffe02"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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