GHSA-3H9H-H4QR-R799

Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 12:30
VLAI
Details

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

batman-adv: mcast: linearize skbuff for packet generation

batadv_mcast_forw_packet() and batadv_mcast_forw_scrape() is not only called (indirectly) by the unsharing+linearizing batadv_recv_mcast_packet() handler. When it is called (indirectly) by batadv_mcast_forw_mcsend() then it will be unshared but not linearized. The SKB_LINEAR_ASSERT() can therefore cause a fatal BUG().

The linearization should happen during the expansion of the head because the scrape function can be hit already during the initial batadv_mcast_forw_mode() selection code:

  • batadv_interface_tx
  • batadv_mcast_forw_mode
  • batadv_mcast_forw_mode_by_count()
  • batadv_mcast_forw_push() -> calls batadv_mcast_forw_expand_head() before everything else
  • batadv_mcast_forw_push_tvlvs()
  • batadv_mcast_forw_push_dests()
  • batadv_mcast_forw_push_adjust_padding()
  • batadv_mcast_forw_scrape()
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89950"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T11:17:05Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbatman-adv: mcast: linearize skbuff for packet generation\n\nbatadv_mcast_forw_packet() and batadv_mcast_forw_scrape() is not only\ncalled (indirectly) by the unsharing+linearizing batadv_recv_mcast_packet()\nhandler. When it is called (indirectly) by batadv_mcast_forw_mcsend() then\nit will be unshared but not linearized. The SKB_LINEAR_ASSERT() can\ntherefore cause a fatal BUG().\n\nThe linearization should happen during the expansion of the head because\nthe scrape function can be hit already during the initial\nbatadv_mcast_forw_mode() selection code:\n\n* batadv_interface_tx\n* batadv_mcast_forw_mode\n* batadv_mcast_forw_mode_by_count()\n* batadv_mcast_forw_push()\n  -\u003e calls batadv_mcast_forw_expand_head() before everything else\n* batadv_mcast_forw_push_tvlvs()\n* batadv_mcast_forw_push_dests()\n* batadv_mcast_forw_push_adjust_padding()\n* batadv_mcast_forw_scrape()",
  "id": "GHSA-3h9h-h4qr-r799",
  "modified": "2026-09-16T12:30:42Z",
  "published": "2026-09-16T12:30:42Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89950"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2879177539e3ece483a8e5406970373698e9a6c5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6a30a59e2660afd03c975f1b8eae6a2301161197"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a9603e0a7cb5e0cddc6b23af153cf7daafc5c55e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c32e5e25c41201c8c3b796a4ab2c45103187091e"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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