Vulnerability-Lookup

CVE-2026-81000 (GCVE-0-2026-81000)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:42 – Updated: 2026-09-11 19:42

Title

net: tun: bound receive headroom

Summary

In the Linux kernel, the following vulnerability has been resolved: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head. Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN. Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.

Severity

No CVSS data available.

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/379d85c7f25f3e05a…
https://git.kernel.org/stable/c/e098d9cc8859614a7…
https://git.kernel.org/stable/c/0ada54ea63e48b9c1…
https://git.kernel.org/stable/c/447c9303942c439a1…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: eaea34b23c46bf17b4a5638be69ab3561854f34b , < 379d85c7f25f3e05a428225e6b8a65613c6e9b9d (git) Affected: eaea34b23c46bf17b4a5638be69ab3561854f34b , < e098d9cc8859614a7f7baebc96e32a5a16b18ed2 (git) Affected: eaea34b23c46bf17b4a5638be69ab3561854f34b , < 0ada54ea63e48b9c1608e917ccb7dfadbe86db28 (git) Affected: eaea34b23c46bf17b4a5638be69ab3561854f34b , < 447c9303942c439a117d9b76ce6d6e2116b38ee7 (git)	guessed
Linux	Linux	Affected: 4.6 Unaffected: 0 , < 4.6 (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
          ],
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          "vendor": "Linux",
          "versions": [
            {
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              "version": "4.6"
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              "versionType": "semver"
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              "versionType": "semver"
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              "version": "7.2.4",
              "versionType": "semver"
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                  "vulnerable": true
                },
                {
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                },
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              "operator": "OR"
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tun: bound receive headroom\n\ntun_get_user() uses tun-\u003ealign both as skb headroom and when choosing how\nmuch packet data to keep linear. OVS can propagate an oversized headroom\nrequest from another port to TUN or TAP.\n\nWhen align is larger than the usable space in a one-page skb head,\nSKB_MAX_HEAD(align) underflows and the result becomes negative when stored\nin good_linear. That value later wraps when assigned to the size_t linear\nvariable, and tun_alloc_skb() can place skb-\u003edata outside the allocated\nhead.\n\nBound the headroom stored by TUN to the one-page skb-head budget and the\nlargest non-sentinel 16-bit skb header offset. Leave one linear byte for\nraw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.\n\nAlso pull the raw-TUN protocol byte and the TAP Ethernet header before\naccessing them, so these checks remain safe for nonlinear skbs supplied by\nother allocation paths."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-11T19:42:54.181Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/379d85c7f25f3e05a428225e6b8a65613c6e9b9d"
        },
        {
          "url": "https://git.kernel.org/stable/c/e098d9cc8859614a7f7baebc96e32a5a16b18ed2"
        },
        {
          "url": "https://git.kernel.org/stable/c/0ada54ea63e48b9c1608e917ccb7dfadbe86db28"
        },
        {
          "url": "https://git.kernel.org/stable/c/447c9303942c439a117d9b76ce6d6e2116b38ee7"
        }
      ],
      "title": "net: tun: bound receive headroom",
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      }
    }
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-81000",
    "datePublished": "2026-09-11T19:42:54.181Z",
    "dateReserved": "2026-08-26T14:34:25.812Z",
    "dateUpdated": "2026-09-11T19:42:54.181Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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    "redhat_vex": {
      "current_release_date": "2026-09-11T21:38:42+00:00",
      "cve": "CVE-2026-81000",
      "id": "CVE-2026-81000",
      "initial_release_date": "2026-09-11T19:42:54.181000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel TUN/TAP: Memory corruption due to oversized headroom request",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-81000.json",
      "version": "3"
    }
  }
}

FKIE_CVE-2026-81000

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-11 20:19

Severity

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/0ada54ea63e48b9c1608e917ccb7dfadbe86db28
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/379d85c7f25f3e05a428225e6b8a65613c6e9b9d
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/447c9303942c439a117d9b76ce6d6e2116b38ee7
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e098d9cc8859614a7f7baebc96e32a5a16b18ed2

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "379d85c7f25f3e05a428225e6b8a65613c6e9b9d",
              "status": "affected",
              "version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
              "versionType": "git"
            },
            {
              "lessThan": "e098d9cc8859614a7f7baebc96e32a5a16b18ed2",
              "status": "affected",
              "version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
              "versionType": "git"
            },
            {
              "lessThan": "0ada54ea63e48b9c1608e917ccb7dfadbe86db28",
              "status": "affected",
              "version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
              "versionType": "git"
            },
            {
              "lessThan": "447c9303942c439a117d9b76ce6d6e2116b38ee7",
              "status": "affected",
              "version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.6"
            },
            {
              "lessThan": "4.6",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "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: tun: bound receive headroom\n\ntun_get_user() uses tun-\u003ealign both as skb headroom and when choosing how\nmuch packet data to keep linear. OVS can propagate an oversized headroom\nrequest from another port to TUN or TAP.\n\nWhen align is larger than the usable space in a one-page skb head,\nSKB_MAX_HEAD(align) underflows and the result becomes negative when stored\nin good_linear. That value later wraps when assigned to the size_t linear\nvariable, and tun_alloc_skb() can place skb-\u003edata outside the allocated\nhead.\n\nBound the headroom stored by TUN to the one-page skb-head budget and the\nlargest non-sentinel 16-bit skb header offset. Leave one linear byte for\nraw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.\n\nAlso pull the raw-TUN protocol byte and the TAP Ethernet header before\naccessing them, so these checks remain safe for nonlinear skbs supplied by\nother allocation paths."
    }
  ],
  "id": "CVE-2026-81000",
  "lastModified": "2026-09-11T20:19:07.710",
  "metrics": {},
  "published": "2026-09-11T20:19:07.710",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0ada54ea63e48b9c1608e917ccb7dfadbe86db28"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/379d85c7f25f3e05a428225e6b8a65613c6e9b9d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/447c9303942c439a117d9b76ce6d6e2116b38ee7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e098d9cc8859614a7f7baebc96e32a5a16b18ed2"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-32HF-VHCC-85C2

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-11 21:31

Details

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

net: tun: bound receive headroom

tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP.

When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head.

Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.

Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-81000"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:07Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tun: bound receive headroom\n\ntun_get_user() uses tun-\u003ealign both as skb headroom and when choosing how\nmuch packet data to keep linear. OVS can propagate an oversized headroom\nrequest from another port to TUN or TAP.\n\nWhen align is larger than the usable space in a one-page skb head,\nSKB_MAX_HEAD(align) underflows and the result becomes negative when stored\nin good_linear. That value later wraps when assigned to the size_t linear\nvariable, and tun_alloc_skb() can place skb-\u003edata outside the allocated\nhead.\n\nBound the headroom stored by TUN to the one-page skb-head budget and the\nlargest non-sentinel 16-bit skb header offset. Leave one linear byte for\nraw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.\n\nAlso pull the raw-TUN protocol byte and the TAP Ethernet header before\naccessing them, so these checks remain safe for nonlinear skbs supplied by\nother allocation paths.",
  "id": "GHSA-32hf-vhcc-85c2",
  "modified": "2026-09-11T21:31:23Z",
  "published": "2026-09-11T21:31:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-81000"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0ada54ea63e48b9c1608e917ccb7dfadbe86db28"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/379d85c7f25f3e05a428225e6b8a65613c6e9b9d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/447c9303942c439a117d9b76ce6d6e2116b38ee7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e098d9cc8859614a7f7baebc96e32a5a16b18ed2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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.

Action not permitted

CVE-2026-81000 (GCVE-0-2026-81000)

FKIE_CVE-2026-81000

GHSA-32HF-VHCC-85C2

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