Vulnerability-Lookup

FKIE_CVE-2026-80612

Vulnerability from fkie_nvd - Published: 2026-08-28 08:16 - Updated: 2026-08-29 07:16

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

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

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/19eec11f3ab5dd29ba58f5f209c24e946c95ef12
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c00320b0e355c4bf0ae4743a53b4180fea237546

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/lwtunnel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "19eec11f3ab5dd29ba58f5f209c24e946c95ef12",
              "status": "affected",
              "version": "8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc",
              "versionType": "git"
            },
            {
              "lessThan": "c00320b0e355c4bf0ae4743a53b4180fea237546",
              "status": "affected",
              "version": "8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/core/lwtunnel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "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-\u003edata. LWT programs cannot\naccess the __sk_buff-\u003edata_meta pseudo-pointer to metadata.\n\nHowever, LWT encapsulation prepends outer headers, moving skb-\u003edata 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-\u003edata. But since\n   the IP output path runs LWT xmit before neighbour output has built\n   the outgoing L2 header, for forwarded packets skb-\u003edata 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-\u003edata, 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   \u003cIRQ\u003e\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   \u003c/IRQ\u003e\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)."
    }
  ],
  "id": "CVE-2026-80612",
  "lastModified": "2026-08-29T07:16:45.997",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-28T08:16:45.183",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/19eec11f3ab5dd29ba58f5f209c24e946c95ef12"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c00320b0e355c4bf0ae4743a53b4180fea237546"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-80612 (GCVE-0-2026-80612)

Vulnerability from cvelistv5 – Published: 2026-08-28 06:48 – Updated: 2026-08-29 06:21

Title

net: lwtunnel: Drop skb metadata before LWT encapsulation

Summary

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/19eec11f3ab5dd29b…
https://git.kernel.org/stable/c/c00320b0e355c4bf0…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc , < 19eec11f3ab5dd29ba58f5f209c24e946c95ef12 (git) Affected: 8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc , < c00320b0e355c4bf0ae4743a53b4180fea237546 (git)
Linux	Linux	Affected: 6.19 Unaffected: 0 , < 6.19 (semver) Unaffected: 7.1.5 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/lwtunnel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "19eec11f3ab5dd29ba58f5f209c24e946c95ef12",
              "status": "affected",
              "version": "8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc",
              "versionType": "git"
            },
            {
              "lessThan": "c00320b0e355c4bf0ae4743a53b4180fea237546",
              "status": "affected",
              "version": "8989d328dfe7c7a3b9f4b9f0ef60006d277f81cc",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/core/lwtunnel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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-\u003edata. LWT programs cannot\naccess the __sk_buff-\u003edata_meta pseudo-pointer to metadata.\n\nHowever, LWT encapsulation prepends outer headers, moving skb-\u003edata 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-\u003edata. But since\n   the IP output path runs LWT xmit before neighbour output has built\n   the outgoing L2 header, for forwarded packets skb-\u003edata 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-\u003edata, 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   \u003cIRQ\u003e\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   \u003c/IRQ\u003e\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)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug fires on the network RX datapath in softirq when remotely sourced packets are received, forwarded, and LWT-encapsulated (ip6_rcv_finish to ip6_forward to lwtunnel_xmit as shown in the fix commit stack trace).\nAC:L - Once a forwarding host has XDP/TC metadata plus LWT encap routes, an attacker can repeatedly send matching traffic and deterministically hit the metadata/encap collision each time without races or victim-timed actions.\nPR:N - The attacker only needs to send IP packets to a forwarding system; LWT routes, XDP/TC metadata programs, and forwarding are administrator deployment choices, not privileges the attacker must hold on the victim.\nUI:N - No end-user interaction is required beyond delivering attacker-controlled network packets to an affected router or edge node.\nS:U - Impact is confined to kernel network packet processing on the same host and does not cross VM, hypervisor, or sandbox security boundaries.\nC:H - Non-BPF LWT encap silently overwrites metadata while meta_len can remain set, and BPF LWT xmit mishandles metadata via skb_data_move, enabling corrupted metadata reads by later BPF/TC code and potential information disclosure.\nI:H - LWT encapsulation performs headroom skb_push/bpf_skb_change_head over the metadata region without clearing meta_len, corrupting skb memory state in ways that can misdirect subsequent kernel/BPF packet-buffer writes.\nA:H - The BPF LWT path triggers skb_data_move WARN_ON_ONCE in softirq and non-BPF encap corrupts forwarding skbs, enabling warn-driven failure modes and repeated disruption of packet forwarding on internet-facing edge routers."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-29T06:21:20.430Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/19eec11f3ab5dd29ba58f5f209c24e946c95ef12"
        },
        {
          "url": "https://git.kernel.org/stable/c/c00320b0e355c4bf0ae4743a53b4180fea237546"
        }
      ],
      "title": "net: lwtunnel: Drop skb metadata before LWT encapsulation",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80612",
    "datePublished": "2026-08-28T06:48:34.527Z",
    "dateReserved": "2026-08-26T14:34:25.773Z",
    "dateUpdated": "2026-08-29T06:21:20.430Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

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FKIE_CVE-2026-80612

CVE-2026-80612 (GCVE-0-2026-80612)

Tags

Sightings

Nomenclature