ipv4: ip_gre: make ipgre_header() robust

{
  "id": "298320dcb6038388611287d8fe82e452640ae632ca56d4b21c04b5e93fa2ea5d",
  "url": "https://osv.dev/vulnerability/CVE-2026-23011",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ipv4: ip_gre: make ipgre_header() robust",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ipv4: ip_gre: make ipgre_header() robust Analog to commit db5b4e39c4e6 (\"ip6_gre: make ip6gre_header() robust\") Over the years, syzbot found many ways to crash the kernel in ipgre_header() [1]. This involves team or bonding drivers ability to dynamically change their dev->needed_headroom and/or dev->hard_header_len In this particular crash mld_newpack() allocated an skb with a too small reserve/headroom, and by the time mld_sendpack() was called, syzbot managed to attach an ipgre device. [1] skbuff: skb_under_panic: text:ffffffff89ea3cb7 len:2030915468 put:2030915372 head:ffff888058b43000 data:ffff887fdfa6e194 tail:0x120 end:0x6c0 dev:team0 kernel BUG at net/core/skbuff.c:213 ! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 1322 Comm: kworker/1:9 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: mld mld_ifc_work RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:213 Call Trace: skb_under_panic net/core/skbuff.c:223 [inline] skb_push+0xc3/0xe0 net/core/skbuff.c:2641 ipgre_header+0x67/0x290 net/ipv4/ip_gre.c:897 dev_hard_header include/linux/netdevice.h:3436 [inline] neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv",
    "evidence": "osv:CVE-2026-23011",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-23011",
      "aliases": [
        "CVE-2026-23011"
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      ],
      "modified": "2026-10-28T02:30:37.300564318Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
        "https://git.kernel.org/stable/c/06fe0801396a36cab865b34f666de1d65bc5ce8e",
        "https://git.kernel.org/stable/c/2ecf0aa7cc262472a9599cc51ba02ada0897a17a",
        "https://git.kernel.org/stable/c/554201ed0a8f4d32e719f42caeaeb2735a9ed6ca",
        "https://git.kernel.org/stable/c/8d5b6b2d79c1c22a5b0db1187a6439dff375a022",
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        "https://git.kernel.org/stable/c/eeb9a521de40c6fadccc12fa5205e5a1b364d5a8",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23011.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23011",
        "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/2026/23xxx/CVE-2026-23011.json"
      }
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    "related_cves": [
      {
        "value": "CVE-2026-23011",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 504833,
  "published_at": "2026-01-25T14:36:24.455+00:00"
}