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CVE-2025-39850

Estado: ModificadaMedia (5.5)—

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

vxlan: Fix NPD in {arp,neigh}_reduce() when using nexthop objects

When the "proxy" option is enabled on a VXLAN device, the device will suppress ARP requests and IPv6 Neighbor Solicitation messages if it is able to reply on behalf of the remote host. That is, if a matching and valid neighbor entry is configured on the VXLAN device whose MAC address is not behind the "any" remote (0.0.0.0 / ::).

The code currently assumes that the FDB entry for the neighbor's MAC address points to a valid remote destination, but this is incorrect if the entry is associated with an FDB nexthop group. This can result in a NPD [1][3] which can be reproduced using [2][4].

Leer descripción completaMostrar menos

Fix by checking that the remote destination exists before dereferencing it.

[2] #!/bin/bash

ip address add 192.0.2.1/32 dev lo

ip nexthop add id 1 via 192.0.2.2 fdb ip nexthop add id 10 group 1 fdb

ip link add name vx0 up type vxlan id 10010 local 192.0.2.1 dstport 4789 proxy

ip neigh add 192.0.2.3 lladdr 00:11:22:33:44:55 nud perm dev vx0

bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10

arping -b -c 1 -s 192.0.2.1 -I vx0 192.0.2.3

[4] #!/bin/bash

ip address add 2001:db8:1::1/128 dev lo

ip nexthop add id 1 via 2001:db8:1::1 fdb ip nexthop add id 10 group 1 fdb

ip link add name vx0 up type vxlan id 10010 local 2001:db8:1::1 dstport 4789 proxy

ip neigh add 2001:db8:1::3 lladdr 00:11:22:33:44:55 nud perm dev vx0

bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10

ndisc6 -r 1 -s 2001:db8:1::1 -w 1 2001:db8:1::3 vx0

Detalles técnicos trazas, registros y código del informe original
[1]
BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
CPU: 4 UID: 0 PID: 365 Comm: arping Not tainted 6.17.0-rc2-virtme-g2a89cb21162c #2 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014
RIP: 0010:vxlan_xmit+0xb58/0x15f0
[...]
Call Trace:
 <TASK>
 dev_hard_start_xmit+0x5d/0x1c0
 __dev_queue_xmit+0x246/0xfd0
 packet_sendmsg+0x113a/0x1850
 __sock_sendmsg+0x38/0x70
 __sys_sendto+0x126/0x180
 __x64_sys_sendto+0x24/0x30
 do_syscall_64+0xa4/0x260
 entry_SYSCALL_64_after_hwframe+0x4b/0x53

[3]
BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
CPU: 13 UID: 0 PID: 372 Comm: ndisc6 Not tainted 6.17.0-rc2-virtmne-g6ee90cb26014 #3 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1v996), BIOS 1.17.0-4.fc41 04/01/2x014
RIP: 0010:vxlan_xmit+0x803/0x1600
[...]
Call Trace:
 <TASK>
 dev_hard_start_xmit+0x5d/0x1c0
 __dev_queue_xmit+0x246/0xfd0
 ip6_finish_output2+0x210/0x6c0
 ip6_finish_output+0x1af/0x2b0
 ip6_mr_output+0x92/0x3e0
 ip6_send_skb+0x30/0x90
 rawv6_sendmsg+0xe6e/0x12e0
 __sock_sendmsg+0x38/0x70
 __sys_sendto+0x126/0x180
 __x64_sys_sendto+0x24/0x30
 do_syscall_64+0xa4/0x260
 entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7f383422ec77

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).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2025-39850",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2025-39850",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-01-14T19:20:51.126279Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.5,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 1.8
      },
      {
        "type": "Secondary",
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.5,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "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": "1274e1cc42264d4e629841e4f182795cb0becfd2",
              "lessThan": "e211e3f4199ac829bd493632efcd131d337cba9d",
              "versionType": "git"
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            {
              "status": "affected",
              "version": "1274e1cc42264d4e629841e4f182795cb0becfd2",
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              "lessThan": "1f5d2fd1ca04a23c18b1bde9a43ce2fa2ffa1bce",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/net/vxlan/vxlan_core.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.8"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "5.8",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.12.46",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.16.6",
              "versionType": "semver",
              "lessThanOrEqual": "6.16.*"
            },
            {
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/net/vxlan/vxlan_core.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2025-09-19T16:15:43.873",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/1f5d2fd1ca04a23c18b1bde9a43ce2fa2ffa1bce",
      "tags": [
        "Patch"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/8cfa0f076842f9b3b4eb52ae0e41d16e25cbf8fa",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/e211e3f4199ac829bd493632efcd131d337cba9d",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ]
    },
    {
      "type": "Secondary",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: Fix NPD in {arp,neigh}_reduce() when using nexthop objects\n\nWhen the \"proxy\" option is enabled on a VXLAN device, the device will\nsuppress ARP requests and IPv6 Neighbor Solicitation messages if it is\nable to reply on behalf of the remote host. That is, if a matching and\nvalid neighbor entry is configured on the VXLAN device whose MAC address\nis not behind the \"any\" remote (0.0.0.0 / ::).\n\nThe code currently assumes that the FDB entry for the neighbor's MAC\naddress points to a valid remote destination, but this is incorrect if\nthe entry is associated with an FDB nexthop group. This can result in a\nNPD [1][3] which can be reproduced using [2][4].\n\nFix by checking that the remote destination exists before dereferencing\nit.\n\n[1]\nBUG: kernel NULL pointer dereference, address: 0000000000000000\n[...]\nCPU: 4 UID: 0 PID: 365 Comm: arping Not tainted 6.17.0-rc2-virtme-g2a89cb21162c #2 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014\nRIP: 0010:vxlan_xmit+0xb58/0x15f0\n[...]\nCall Trace:\n <TASK>\n dev_hard_start_xmit+0x5d/0x1c0\n __dev_queue_xmit+0x246/0xfd0\n packet_sendmsg+0x113a/0x1850\n __sock_sendmsg+0x38/0x70\n __sys_sendto+0x126/0x180\n __x64_sys_sendto+0x24/0x30\n do_syscall_64+0xa4/0x260\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\n[2]\n #!/bin/bash\n\n ip address add 192.0.2.1/32 dev lo\n\n ip nexthop add id 1 via 192.0.2.2 fdb\n ip nexthop add id 10 group 1 fdb\n\n ip link add name vx0 up type vxlan id 10010 local 192.0.2.1 dstport 4789 proxy\n\n ip neigh add 192.0.2.3 lladdr 00:11:22:33:44:55 nud perm dev vx0\n\n bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10\n\n arping -b -c 1 -s 192.0.2.1 -I vx0 192.0.2.3\n\n[3]\nBUG: kernel NULL pointer dereference, address: 0000000000000000\n[...]\nCPU: 13 UID: 0 PID: 372 Comm: ndisc6 Not tainted 6.17.0-rc2-virtmne-g6ee90cb26014 #3 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1v996), BIOS 1.17.0-4.fc41 04/01/2x014\nRIP: 0010:vxlan_xmit+0x803/0x1600\n[...]\nCall Trace:\n <TASK>\n dev_hard_start_xmit+0x5d/0x1c0\n __dev_queue_xmit+0x246/0xfd0\n ip6_finish_output2+0x210/0x6c0\n ip6_finish_output+0x1af/0x2b0\n ip6_mr_output+0x92/0x3e0\n ip6_send_skb+0x30/0x90\n rawv6_sendmsg+0xe6e/0x12e0\n __sock_sendmsg+0x38/0x70\n __sys_sendto+0x126/0x180\n __x64_sys_sendto+0x24/0x30\n do_syscall_64+0xa4/0x260\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\nRIP: 0033:0x7f383422ec77\n\n[4]\n #!/bin/bash\n\n ip address add 2001:db8:1::1/128 dev lo\n\n ip nexthop add id 1 via 2001:db8:1::1 fdb\n ip nexthop add id 10 group 1 fdb\n\n ip link add name vx0 up type vxlan id 10010 local 2001:db8:1::1 dstport 4789 proxy\n\n ip neigh add 2001:db8:1::3 lladdr 00:11:22:33:44:55 nud perm dev vx0\n\n bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10\n\n ndisc6 -r 1 -s 2001:db8:1::1 -w 1 2001:db8:1::3 vx0"
    }
  ],
  "lastModified": "2026-06-17T09:18:37.360",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "2980C061-51F5-499C-B8BE-47E98D17CE4B",
              "versionEndExcluding": "6.12.46",
              "versionStartIncluding": "5.8"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "548F104C-0F08-438B-9C97-64C903F0C678",
              "versionEndExcluding": "6.16.6",
              "versionStartIncluding": "6.13"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C"
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              "vulnerable": true,
              "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9"
            },
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              "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "39982C4B-716E-4B2F-8196-FA301F47807D"
            },
            {
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              "vulnerable": true,
              "matchCriteriaId": "340BEEA9-D70D-4290-B502-FBB1032353B1"
            }
          ],
          "operator": "OR"
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      ]
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}