CVE-2026-80612

Estado: RecibidaCrítica (9.8)—

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

net: lwtunnel: Drop skb metadata before LWT encapsulation

skb metadata is meant for passing information between XDP and TC. It lives in the skb headroom, immediately before skb->data. LWT programs cannot access the __sk_buff->data_meta pseudo-pointer to metadata.

However, LWT encapsulation prepends outer headers, moving skb->data back over the headroom where the metadata sits. On an RX-originated (forwarded) packet that still carries XDP metadata this goes wrong in two different ways, depending on the encap type:

That is what happens, as for how to fix it - a received packet that carries metadata can reach an encap through any of the three LWT redirect modes:

Leer descripción completaMostrar menos

Every encap funnels through the three LWT dispatch helpers, so drop the metadata there, right before handing the skb to the encap op. This single chokepoint covers all encap types and all three redirect modes:

Alternatively, we could clear the metadata right after TC ingress hook. That would require a compromise, however. Metadata would become inaccessible from TC egress (in setups where it actually reaches the hook it tact, that is without any L2 tunnels on path).

Detalles técnicos trazas, registros y código del informe original

1. Non-BPF LWT encaps (mpls, seg6, ioam6 ...) call skb_push()/skb_pull()
   and silently overwrite the metadata that sits in the headroom.

2) BPF LWT xmit calls bpf_skb_change_head(), which uses skb_data_move().
   That helper expects metadata immediately before skb->data. But since
   the IP output path runs LWT xmit before neighbour output has built
   the outgoing L2 header, for forwarded packets skb->data points at the
   L3 header while skb_mac_header() still points at the old L2 header.
   skb_data_move() sees metadata ending at skb_mac_header(), not before
   skb->data, warns and clears metadata:

  WARNING: CPU: 21 PID: 454557 at include/linux/skbuff.h:4609 skb_data_move+0x47/0x90
  CPU: 21 UID: 0 PID: 454557 Comm: napi/iconduit-g Tainted: G           O        6.18.21 #1
  RIP: 0010:skb_data_move+0x47/0x90
  Call Trace:
   <IRQ>
   bpf_skb_change_head+0xe6/0x1a0
   bpf_prog_...+0x213/0x2e3
   run_lwt_bpf.isra.0+0x1d3/0x360
   bpf_xmit+0x46/0xe0
   lwtunnel_xmit+0xa1/0xf0
   ip_finish_output2+0x1e7/0x5e0
   ip_output+0x63/0x100
   __netif_receive_skb_one_core+0x85/0xa0
   process_backlog+0x9c/0x150
   __napi_poll+0x2b/0x190
   net_rx_action+0x40b/0x7f0
   handle_softirqs+0xd2/0x270
   do_softirq+0x3f/0x60
   </IRQ>

  LWTUNNEL_STATE_INPUT_REDIRECT
   ip6_rcv_finish
     dst_input
       lwtunnel_input

  LWTUNNEL_STATE_OUTPUT_REDIRECT
   ip6_rcv_finish
     dst_input
       ip6_forward
         ip6_forward_finish
           dst_output
             lwtunnel_output

  LWTUNNEL_STATE_XMIT_REDIRECT
   ip6_rcv_finish
     dst_input
       ip6_forward
         ip6_forward_finish
           dst_output
             ip6_output
               ip6_finish_output
                 ip6_finish_output2
                   lwtunnel_xmit

  - lwtunnel_input():  seg6, rpl, ila, seg6_local
  - lwtunnel_output(): ioam6
  - lwtunnel_xmit():   mpls, LWT BPF xmit

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 9.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.55%
Percentil entre todas las CVEs puntuadas: 44
Fecha de la puntuación: 6/10/2026

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.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access75 %

Vector CVSS AV:N/AC:L/PR:N indica explotación remota sin privilegios (T1190). El bug causa corrupción de metadatos en paquetes de red, resultando en DoS (T1499.004) y posible corrupción de datos (T1565.001) en el procesamiento de túneles.

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

Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Filter Network Traffic Application Isolation and Sandboxing

Tecnologías afectadas (1)

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

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-80612",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.8,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "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": "8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc",
              "lessThan": "19eec11f3ab5dd29ba58f5f209c24e946c95ef12",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc",
              "lessThan": "c00320b0e355c4bf0ae4743a53b4180fea237546",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "net/core/lwtunnel.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.19",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver",
              "lessThanOrEqual": "7.1.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "net/core/lwtunnel.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-28T08:16:45.183",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/19eec11f3ab5dd29ba58f5f209c24e946c95ef12",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/c00320b0e355c4bf0ae4743a53b4180fea237546",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: lwtunnel: Drop skb metadata before LWT encapsulation\n\nskb metadata is meant for passing information between XDP and TC. It lives\nin the skb headroom, immediately before skb->data. LWT programs cannot\naccess the __sk_buff->data_meta pseudo-pointer to metadata.\n\nHowever, LWT encapsulation prepends outer headers, moving skb->data back\nover the headroom where the metadata sits. On an RX-originated (forwarded)\npacket that still carries XDP metadata this goes wrong in two different\nways, depending on the encap type:\n\n1. Non-BPF LWT encaps (mpls, seg6, ioam6 ...) call skb_push()/skb_pull()\n   and silently overwrite the metadata that sits in the headroom.\n\n2) BPF LWT xmit calls bpf_skb_change_head(), which uses skb_data_move().\n   That helper expects metadata immediately before skb->data. But since\n   the IP output path runs LWT xmit before neighbour output has built\n   the outgoing L2 header, for forwarded packets skb->data points at the\n   L3 header while skb_mac_header() still points at the old L2 header.\n   skb_data_move() sees metadata ending at skb_mac_header(), not before\n   skb->data, warns and clears metadata:\n\n  WARNING: CPU: 21 PID: 454557 at include/linux/skbuff.h:4609 skb_data_move+0x47/0x90\n  CPU: 21 UID: 0 PID: 454557 Comm: napi/iconduit-g Tainted: G           O        6.18.21 #1\n  RIP: 0010:skb_data_move+0x47/0x90\n  Call Trace:\n   <IRQ>\n   bpf_skb_change_head+0xe6/0x1a0\n   bpf_prog_...+0x213/0x2e3\n   run_lwt_bpf.isra.0+0x1d3/0x360\n   bpf_xmit+0x46/0xe0\n   lwtunnel_xmit+0xa1/0xf0\n   ip_finish_output2+0x1e7/0x5e0\n   ip_output+0x63/0x100\n   __netif_receive_skb_one_core+0x85/0xa0\n   process_backlog+0x9c/0x150\n   __napi_poll+0x2b/0x190\n   net_rx_action+0x40b/0x7f0\n   handle_softirqs+0xd2/0x270\n   do_softirq+0x3f/0x60\n   </IRQ>\n\nThat is what happens, as for how to fix it - a received packet that\ncarries metadata can reach an encap through any of the three LWT\nredirect modes:\n\n  LWTUNNEL_STATE_INPUT_REDIRECT\n   ip6_rcv_finish\n     dst_input\n       lwtunnel_input\n\n  LWTUNNEL_STATE_OUTPUT_REDIRECT\n   ip6_rcv_finish\n     dst_input\n       ip6_forward\n         ip6_forward_finish\n           dst_output\n             lwtunnel_output\n\n  LWTUNNEL_STATE_XMIT_REDIRECT\n   ip6_rcv_finish\n     dst_input\n       ip6_forward\n         ip6_forward_finish\n           dst_output\n             ip6_output\n               ip6_finish_output\n                 ip6_finish_output2\n                   lwtunnel_xmit\n\nEvery encap funnels through the three LWT dispatch helpers, so drop the\nmetadata there, right before handing the skb to the encap op. This\nsingle chokepoint covers all encap types and all three redirect modes:\n\n  - lwtunnel_input():  seg6, rpl, ila, seg6_local\n  - lwtunnel_output(): ioam6\n  - lwtunnel_xmit():   mpls, LWT BPF xmit\n\nAlternatively, we could clear the metadata right after TC ingress hook.\nThat would require a compromise, however. Metadata would become\ninaccessible from TC egress (in setups where it actually reaches the\nhook it tact, that is without any L2 tunnels on path)."
    }
  ],
  "lastModified": "2026-08-29T07:16:45.997",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}