Vulnerability-Lookup

GHSA-5QFP-9H7G-RCPM

Vulnerability from github – Published: 2026-08-27 06:31 – Updated: 2026-08-27 06:31

Details

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

macvlan: inherit needed_headroom and needed_tailroom from lowerdev

macvlan devices inherit hard_header_len from lowerdev during macvlan_init(), but leave needed_headroom and needed_tailroom set to 0.

When the underlying lowerdev requires extra headroom or tailroom for headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx headroom), upper layers calculating packet headroom and tailroom fail to reserve sufficient space.

This can result in reallocation overhead, skb headroom underflows, or KASAN slab-use-after-free crashes when dev_hard_header() / macvlan_hard_header() prepends header data or when lower devices append tailroom.

Fix this by: 1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached macvlans in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.

Severity

9.8 (Critical)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74743"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-26T15:16:53Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmacvlan: inherit needed_headroom and needed_tailroom from lowerdev\n\nmacvlan devices inherit hard_header_len from lowerdev during macvlan_init(),\nbut leave needed_headroom and needed_tailroom set to 0.\n\nWhen the underlying lowerdev requires extra headroom or tailroom for\nheaders/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx\nheadroom), upper layers calculating packet headroom and tailroom fail to\nreserve sufficient space.\n\nThis can result in reallocation overhead, skb headroom underflows, or KASAN\nslab-use-after-free crashes when dev_hard_header() / macvlan_hard_header()\nprepends header data or when lower devices append tailroom.\n\nFix this by:\n1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init().\n2. Propagating needed_headroom and needed_tailroom updates to attached macvlans\n   in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.",
  "id": "GHSA-5qfp-9h7g-rcpm",
  "modified": "2026-08-27T06:31:30Z",
  "published": "2026-08-27T06:31:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74743"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/28afc87bd8da0b3348bbbd834c8a89e83712cf5e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8cd90e850e434577bf6774778657d26d6995e53f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8f6a05dbac05725e0786701eb04778c5bdbe4eaa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/96fa90b74385b7f2b0d97251dd43d5ee6ca44668"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bc9a00fb78e32bccc39d763bfd13a450705bac5d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cef51860becd9700217c81732ca1eb1ea6ed6fe1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-74743 (GCVE-0-2026-74743)

Vulnerability from cvelistv5 – Published: 2026-08-26 14:36 – Updated: 2026-08-27 05:01

Title

macvlan: inherit needed_headroom and needed_tailroom from lowerdev

Summary

In the Linux kernel, the following vulnerability has been resolved: macvlan: inherit needed_headroom and needed_tailroom from lowerdev macvlan devices inherit hard_header_len from lowerdev during macvlan_init(), but leave needed_headroom and needed_tailroom set to 0. When the underlying lowerdev requires extra headroom or tailroom for headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx headroom), upper layers calculating packet headroom and tailroom fail to reserve sufficient space. This can result in reallocation overhead, skb headroom underflows, or KASAN slab-use-after-free crashes when dev_hard_header() / macvlan_hard_header() prepends header data or when lower devices append tailroom. Fix this by: 1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached macvlans in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.

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

6 references

URL	Tags
https://git.kernel.org/stable/c/8cd90e850e434577b…
https://git.kernel.org/stable/c/28afc87bd8da0b334…
https://git.kernel.org/stable/c/8f6a05dbac05725e0…
https://git.kernel.org/stable/c/96fa90b74385b7f2b…
https://git.kernel.org/stable/c/bc9a00fb78e32bccc…
https://git.kernel.org/stable/c/cef51860becd97002…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 , < 8cd90e850e434577bf6774778657d26d6995e53f (git) Affected: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 , < 28afc87bd8da0b3348bbbd834c8a89e83712cf5e (git) Affected: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 , < 8f6a05dbac05725e0786701eb04778c5bdbe4eaa (git) Affected: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 , < 96fa90b74385b7f2b0d97251dd43d5ee6ca44668 (git) Affected: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 , < bc9a00fb78e32bccc39d763bfd13a450705bac5d (git) Affected: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 , < cef51860becd9700217c81732ca1eb1ea6ed6fe1 (git)
Linux	Linux	Affected: 2.6.23 Unaffected: 0 , < 2.6.23 (semver) Unaffected: 6.1.184 , ≤ 6.1.* (semver) Unaffected: 6.6.153 , ≤ 6.6.* (semver) Unaffected: 6.12.105 , ≤ 6.12.* (semver) Unaffected: 6.18.46 , ≤ 6.18.* (semver) Unaffected: 7.1.10 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/macvlan.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "8cd90e850e434577bf6774778657d26d6995e53f",
              "status": "affected",
              "version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
              "versionType": "git"
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              "versionType": "git"
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              "version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
              "versionType": "git"
            }
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.184",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.153",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.105",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.46",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.10",
              "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": "6.1.184",
                  "versionStartIncluding": "2.6.23",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                },
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                }
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              "negate": false,
              "operator": "OR"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmacvlan: inherit needed_headroom and needed_tailroom from lowerdev\n\nmacvlan devices inherit hard_header_len from lowerdev during macvlan_init(),\nbut leave needed_headroom and needed_tailroom set to 0.\n\nWhen the underlying lowerdev requires extra headroom or tailroom for\nheaders/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx\nheadroom), upper layers calculating packet headroom and tailroom fail to\nreserve sufficient space.\n\nThis can result in reallocation overhead, skb headroom underflows, or KASAN\nslab-use-after-free crashes when dev_hard_header() / macvlan_hard_header()\nprepends header data or when lower devices append tailroom.\n\nFix this by:\n1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init().\n2. Propagating needed_headroom and needed_tailroom updates to attached macvlans\n   in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events."
        }
      ],
      "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 macvlan transmit path (ip_finish_output2/neigh_resolve_output/macvlan_hard_header) when kernel-generated replies or forwarded traffic egress a macvlan netdev; remote peers trigger this by sending TCP/UDP/ICMP to an address on a pre-configured macvlan interface.\nAC:L - Once macvlan is stacked on a lowerdev with nonzero needed_headroom (WireGuard, MACsec, IPsec, tunnels, veth RX headroom), ordinary packets reliably hit under-reserved skb headroom/tailroom during dev_hard_header() without races or uncontrollable timing.\nPR:N - A remote attacker needs no local account or capabilities; sending routable traffic to a macvlan address suffices. Administrative macvlan setup is environmental (like other netdev CVEs), not an attacker privilege requirement.\nUI:N - Exploitation requires only normal network delivery to a reachable macvlan address; no victim must open files, mount filesystems, or perform any interactive action beyond existing connectivity.\nS:U - Impact is kernel skb heap corruption, slab-use-after-free, or panic within the host network stack; it does not cross VM, IOMMU, or container security boundaries into a separate authority.\nC:H - The fix commit documents KASAN slab-use-after-free from skb headroom underflow during header prepending; this class of kernel heap corruption is exploitable for arbitrary memory disclosure beyond a bounded leak.\nI:H - Insufficient headroom causes skb_push underflows and slab UAF during pskb_expand_head/reallocation, providing kernel heap write primitives that can be leveraged for control-flow hijacking and privilege escalation.\nA:H - The failure mode includes skb_under_panic (kernel BUG/panic) and KASAN-detected slab UAF crashes, causing immediate host kernel denial of service on affected transmit paths."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-27T05:01:04.222Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/8cd90e850e434577bf6774778657d26d6995e53f"
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        {
          "url": "https://git.kernel.org/stable/c/28afc87bd8da0b3348bbbd834c8a89e83712cf5e"
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        },
        {
          "url": "https://git.kernel.org/stable/c/96fa90b74385b7f2b0d97251dd43d5ee6ca44668"
        },
        {
          "url": "https://git.kernel.org/stable/c/bc9a00fb78e32bccc39d763bfd13a450705bac5d"
        },
        {
          "url": "https://git.kernel.org/stable/c/cef51860becd9700217c81732ca1eb1ea6ed6fe1"
        }
      ],
      "title": "macvlan: inherit needed_headroom and needed_tailroom from lowerdev",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74743",
    "datePublished": "2026-08-26T14:36:54.175Z",
    "dateReserved": "2026-08-15T05:44:03.930Z",
    "dateUpdated": "2026-08-27T05:01:04.222Z",
    "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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GHSA-5QFP-9H7G-RCPM

CVE-2026-74743 (GCVE-0-2026-74743)

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Sightings

Nomenclature