CVE-2026-99041 (GCVE-0-2026-99041)
Vulnerability from cvelistv5
Published
2026-10-23 12:22
Modified
2026-10-30 12:41
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: ip6_gre: remove obsolete ERSPAN PMTU update A tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb, and mirred can redirect it to a native ip6erspan device. The legacy PMTU update in ip6erspan_tunnel_xmit() treats that metadata dst as a route. Since it has no output device, dst_dev(dst)->mtu dereferences NULL. On v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used self-created user and network namespaces to trigger: KASAN: null-ptr-deref RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0 Kernel panic - not syncing: Fatal exception in interrupt The update is obsolete. Commit fe1a4ca0a2b7 ("ip6_gre: process toobig in a better way") changed IPv6 GRE Too Big handling to update the underlay route and removed the equivalent block from __gre6_xmit(). ip6_tnl_xmit() then propagates the underlay PMTU to the overlay route. Remove the stale ERSPAN copy and its now-unused dst variable. This eliminates the metadata-dst dereference and keeps ERSPAN aligned with IPv6 GRE PMTU handling.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
Version: 5a963eb61b7c39e6c422b6e48619d19d04719358
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6_gre: remove obsolete ERSPAN PMTU update\n\nA tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb,\nand mirred can redirect it to a native ip6erspan device. The legacy PMTU\nupdate in ip6erspan_tunnel_xmit() treats that metadata dst as a route.\nSince it has no output device, dst_dev(dst)-\u003emtu dereferences NULL.\n\nOn v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used\nself-created user and network namespaces to trigger:\n\n  KASAN: null-ptr-deref\n  RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe update is obsolete. Commit fe1a4ca0a2b7 (\"ip6_gre: process toobig\nin a better way\") changed IPv6 GRE Too Big handling to update the\nunderlay route and removed the equivalent block from __gre6_xmit().\nip6_tnl_xmit() then propagates the underlay PMTU to the overlay route.\n\nRemove the stale ERSPAN copy and its now-unused dst variable. This\neliminates the metadata-dst dereference and keeps ERSPAN aligned with\nIPv6 GRE PMTU handling."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-30T12:41:14.790Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/ba72ed1c8476ce68eb7152dfcbc5330cefcbaa91"
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        {
          "url": "https://git.kernel.org/stable/c/8bc60db48e8cba35488bbd6e1f94aa990afa275a"
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      "title": "ip6_gre: remove obsolete ERSPAN PMTU update",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99041",
    "datePublished": "2026-10-23T12:22:00.403Z",
    "dateReserved": "2026-09-25T10:25:14.387Z",
    "dateUpdated": "2026-10-30T12:41:14.790Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2"
}


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