netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment()

{
  "id": "fccbd6e25d7e04435a92fc9284e502d021c65c2e91991b98a87242359d97be52",
  "url": "https://osv.dev/vulnerability/CVE-2026-64554",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment() br_ip6_fragment() gets prevhdr, a pointer into the skb head, from ip6_find_1stfragopt(), then calls skb_checksum_help(). For a cloned skb skb_checksum_help() reallocates the head via pskb_expand_head(), leaving prevhdr dangling. It is later dereferenced in ip6_frag_next(), causing a use-after-free write. Save prevhdr's offset before skb_checksum_help() and recompute it after, like commit ef0efcd3bd3f (\"ipv6: Fix dangling pointer when ipv6 fragment\"). BUG: KASAN: slab-use-after-free in ip6_frag_next (net/ipv6/ip6_output.c:857) Write of size 1 at addr ffff888013ff5016 by task exploit/141 Call Trace: ... kasan_report (mm/kasan/report.c:595) ip6_frag_next (net/ipv6/ip6_output.c:857) br_ip6_fragment (net/ipv6/netfilter.c:212) nf_ct_bridge_post (net/bridge/netfilter/nf_conntrack_bridge.c:407) nf_hook_slow (net/netfilter/core.c:619) br_forward_finish (net/bridge/br_forward.c:66) __br_forward (net/bridge/br_forward.c:115) maybe_deliver (net/bridge/br_forward.c:191) br_flood (net/bridge/br_forward.c:245) br_handle_frame_finish (net/bridge/br_input.c:229) br_handle_frame (net/bridge/br_input.c:442) ... packet_sendmsg (net/packet/af_packet.c:3114) ... do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt",
    "evidence": "osv:CVE-2026-64554",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "5.10.261",
            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
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        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-64554",
      "aliases": [
        "CVE-2026-64554"
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      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
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      "affected": [
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      ],
      "modified": "2026-10-28T02:30:52.973811252Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/00c06ef8c018493943891a7d0ca82b71b24f3180",
        "https://git.kernel.org/stable/c/1c4f67c89fd27c4df4c70b135c2c59627698b3c0",
        "https://git.kernel.org/stable/c/2731efa6364e47934c96eb69e01ea131e8af8030",
        "https://git.kernel.org/stable/c/4ac981a8b7ce7aec99a52d08f8a8953e8e120067",
        "https://git.kernel.org/stable/c/86f3ce81dd2b4b0aa2c3016c989a943e4b1b643d",
        "https://git.kernel.org/stable/c/8c10778ec674b67a07ea042fcba64270f3f38a5a",
        "https://git.kernel.org/stable/c/c141f69d0a0fb16964dbc293650047e69bda8af7",
        "https://git.kernel.org/stable/c/f2e6596d10783557aeb9668da2a3b4d19deb2001",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64554.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64554",
        "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/2026/64xxx/CVE-2026-64554.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64554",
        "evidence": "/id"
      }
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521876,
  "published_at": "2026-07-27T20:10:41.726+00:00"
}