gue: Fix skb memleak with inner IP protocol 0.

{
  "id": "05db87ec23858fd70ccdde73163999e147734c0e22a6e0080507cfa94a0b832e",
  "url": "https://osv.dev/vulnerability/CVE-2026-23095",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "gue: Fix skb memleak with inner IP protocol 0.",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: gue: Fix skb memleak with inner IP protocol 0. syzbot reported skb memleak below. [0] The repro generated a GUE packet with its inner protocol 0. gue_udp_recv() returns -guehdr->proto_ctype for \"resubmit\" in ip_protocol_deliver_rcu(), but this only works with non-zero protocol number. Let's drop such packets. Note that 0 is a valid number (IPv6 Hop-by-Hop Option). I think it is not practical to encap HOPOPT in GUE, so once someone starts to complain, we could pass down a resubmit flag pointer to distinguish two zeros from the upper layer: * no error * resubmit HOPOPT [0] BUG: memory leak unreferenced object 0xffff888109695a00 (size 240): comm \"syz.0.17\", pid 6088, jiffies 4294943096 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 40 c2 10 81 88 ff ff 00 00 00 00 00 00 00 00 .@.............. backtrace (crc a84b336f): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270 __build_skb+0x23/0x60 net/core/skbuff.c:474 build_skb+0x20/0x190 net/core/skbuff.c:490 __tun_build_skb drivers/net/tun.c:1541 [inline] tun_build_skb+0x4a1/0xa40 drivers/net/tun.c:1636 tun_get_user+0xc12/0x2030 drivers/net/tun.c:1770 tun_chr_write_iter+0x71/0x120 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x45d/0x710 fs/read",
    "evidence": "osv:CVE-2026-23095",
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    "severity": "high",
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      "aliases": [
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      "metrics": [
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          "type": "CVSS_V3",
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      "modified": "2026-10-28T02:30:50.031794580Z",
      "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/380a82d36e37db49fd41ecc378c22fd29392e96a",
        "https://git.kernel.org/stable/c/536f5bbc322eb1e175bdd1ced22b236a951c4d8f",
        "https://git.kernel.org/stable/c/5437a279804ced8088cabb945dba88a26d828f8c",
        "https://git.kernel.org/stable/c/886f186328b718400dbf79e1bc8cbcbd710ab766",
        "https://git.kernel.org/stable/c/9a56796ad258786d3624eef5aefba394fc9bdded",
        "https://git.kernel.org/stable/c/ce569b389a5c78d64788a5ea94560e17fa574b35",
        "https://git.kernel.org/stable/c/f87b9b7a618c82e7465e872eb10e14c803871892",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23095.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23095",
        "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-2026-23095.json"
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    "related_cves": [
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        "value": "CVE-2026-23095",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518581,
  "published_at": "2026-02-04T16:08:17.99+00:00"
}