mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations

{
  "id": "fd7ce7ff2fb0cd3021b5351d604dfbd7433cea6b8353e07f0c0fa0122ce8f379",
  "url": "https://osv.dev/vulnerability/CVE-2026-31394",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations ieee80211_chan_bw_change() iterates all stations and accesses link->reserved.oper via sta->sdata->link[link_id]. For stations on AP_VLAN interfaces (e.g. 4addr WDS clients), sta->sdata points to the VLAN sdata, whose link never participates in chanctx reservations. This leaves link->reserved.oper zero-initialized with chan == NULL, causing a NULL pointer dereference in __ieee80211_sta_cap_rx_bw() when accessing chandef->chan->band during CSA. Resolve the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data. [also change sta->sdata in ARRAY_SIZE even if it doesn't matter]",
    "evidence": "osv:CVE-2026-31394",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.78",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.20",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.10",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-31394",
      "aliases": [
        "CVE-2026-31394"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "fixed": "65c25b588994dd422fea73fa322de56e1ae4a33b"
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                  "fixed": "5a86d4e920d9783a198e39cf53f0e410fba5fbd6"
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                {
                  "fixed": "3c6629e859a2211a1fbb4868f915413f80001ca5"
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                {
                  "fixed": "672e5229e1ecfc2a3509b53adcb914d8b024a853"
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31394.json"
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        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.11.0"
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                {
                  "fixed": "6.12.78"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.20"
                }
              ]
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            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.10"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31394.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.460490877Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3c6629e859a2211a1fbb4868f915413f80001ca5",
        "https://git.kernel.org/stable/c/5a86d4e920d9783a198e39cf53f0e410fba5fbd6",
        "https://git.kernel.org/stable/c/65c25b588994dd422fea73fa322de56e1ae4a33b",
        "https://git.kernel.org/stable/c/672e5229e1ecfc2a3509b53adcb914d8b024a853",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31394.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31394",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31394.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31394",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 492724,
  "published_at": "2026-04-03T15:15:58.806+00:00"
}