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CVE-2025-39986

Estado: AplazadaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow

Sending an PF_PACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PF_PACKET framework is to make sure that skb->len fits the interface's MTU.

Unfortunately, because the sun4i_can driver does not populate its net_device_ops->ndo_change_mtu(), it is possible for an attacker to configure an invalid MTU by doing, for example:

After doing so, the attacker could open a PF_PACKET socket using the ETH_P_CANXL protocol:

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to inject a malicious CAN XL frames. For example:

The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks:

And so, sun4ican_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame.

This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on this line:

Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs a couple line below when doing:

Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU. By fixing the root cause, this prevents the buffer overflow.

Detalles técnicos trazas, registros y código del informe original
  $ ip link set can0 mtu 9999

	socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))

	struct canxl_frame frame = {
		.flags = 0xff,
		.len = 2048,
	};

  1. the skb->protocol is set to ETH_P_CANXL which is valid (the
     function does not check the actual device capabilities).

  2. the length is a valid CAN XL length.

	dlc = cf->len;

	for (i = 0; i < dlc; i++)
		writel(cf->data[i], priv->base + (dreg + i * 4));

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Acceso local (AV:L) sin interacción del usuario (UI:N) con privilegios (PR:L) permite escalada mediante buffer overflow en sun4i_can. El atacante modifica MTU e inyecta frames maliciosos causando corrupción de memoria del kernel.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence ProgramRestrict File and Directory PermissionsRemote Data StorageFilter Network TrafficExecution PreventionEncrypt Sensitive Information

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux KernelAI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2025-39986",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "063539db42203b29d5aa2adf0cae3d68c646a6b6",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "4f382cc887adca8478b9d3e6b81aa6698a95fff4",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "60463a1c138900494cb3adae41142a11cd8feb3c",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "a61ff7ac93270d20ca426c027d6d01c8ac8e904c",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "2e423e1990f3972cbea779883fef52c2f2acb858",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "de77841652e57afbc46e9e1dbf51ee364fc008e1",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "7f7b21026a6febdb749f6f6f950427245aa86cce",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0738eff14d817a02ab082c392c96a1613006f158",
              "lessThan": "61da0bd4102c459823fbe6b8b43b01fb6ace4a22",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/net/can/sun4i_can.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.4"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "4.4",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.4.300",
              "versionType": "semver",
              "lessThanOrEqual": "5.4.*"
            },
            {
              "status": "unaffected",
              "version": "5.10.245",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "status": "unaffected",
              "version": "5.15.194",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.1.155",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.109",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.50",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.16.10",
              "versionType": "semver",
              "lessThanOrEqual": "6.16.*"
            },
            {
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/net/can/sun4i_can.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2025-10-15T08:15:36.653",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/063539db42203b29d5aa2adf0cae3d68c646a6b6",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/2e423e1990f3972cbea779883fef52c2f2acb858",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4f382cc887adca8478b9d3e6b81aa6698a95fff4",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/60463a1c138900494cb3adae41142a11cd8feb3c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/61da0bd4102c459823fbe6b8b43b01fb6ace4a22",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/7f7b21026a6febdb749f6f6f950427245aa86cce",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a61ff7ac93270d20ca426c027d6d01c8ac8e904c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/de77841652e57afbc46e9e1dbf51ee364fc008e1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Deferred",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow\n\nSending an PF_PACKET allows to bypass the CAN framework logic and to\ndirectly reach the xmit() function of a CAN driver. The only check\nwhich is performed by the PF_PACKET framework is to make sure that\nskb->len fits the interface's MTU.\n\nUnfortunately, because the sun4i_can driver does not populate its\nnet_device_ops->ndo_change_mtu(), it is possible for an attacker to\nconfigure an invalid MTU by doing, for example:\n\n  $ ip link set can0 mtu 9999\n\nAfter doing so, the attacker could open a PF_PACKET socket using the\nETH_P_CANXL protocol:\n\n\tsocket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))\n\nto inject a malicious CAN XL frames. For example:\n\n\tstruct canxl_frame frame = {\n\t\t.flags = 0xff,\n\t\t.len = 2048,\n\t};\n\nThe CAN drivers' xmit() function are calling can_dev_dropped_skb() to\ncheck that the skb is valid, unfortunately under above conditions, the\nmalicious packet is able to go through can_dev_dropped_skb() checks:\n\n  1. the skb->protocol is set to ETH_P_CANXL which is valid (the\n     function does not check the actual device capabilities).\n\n  2. the length is a valid CAN XL length.\n\nAnd so, sun4ican_start_xmit() receives a CAN XL frame which it is not\nable to correctly handle and will thus misinterpret it as a CAN frame.\n\nThis can result in a buffer overflow. The driver will consume cf->len\nas-is with no further checks on this line:\n\n\tdlc = cf->len;\n\nHere, cf->len corresponds to the flags field of the CAN XL frame. In\nour previous example, we set canxl_frame->flags to 0xff. Because the\nmaximum expected length is 8, a buffer overflow of 247 bytes occurs a\ncouple line below when doing:\n\n\tfor (i = 0; i < dlc; i++)\n\t\twritel(cf->data[i], priv->base + (dreg + i * 4));\n\nPopulate net_device_ops->ndo_change_mtu() to ensure that the\ninterface's MTU can not be set to anything bigger than CAN_MTU. By\nfixing the root cause, this prevents the buffer overflow."
    }
  ],
  "lastModified": "2026-07-30T06:24:04.647",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}