GHSA-435J-Q3FF-8922

Vulnerability from github – Published: 2026-07-27 21:31 – Updated: 2026-07-27 21:31
VLAI
Details

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64554"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-27T21:17:08Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment()\n\nbr_ip6_fragment() gets prevhdr, a pointer into the skb head, from\nip6_find_1stfragopt(), then calls skb_checksum_help().  For a cloned skb\nskb_checksum_help() reallocates the head via pskb_expand_head(), leaving\nprevhdr dangling.  It is later dereferenced in ip6_frag_next(), causing a\nuse-after-free write.\n\nSave prevhdr\u0027s offset before skb_checksum_help() and recompute it after,\nlike commit ef0efcd3bd3f (\"ipv6: Fix dangling pointer when ipv6\nfragment\").\n\n  BUG: KASAN: slab-use-after-free in ip6_frag_next (net/ipv6/ip6_output.c:857)\n  Write of size 1 at addr ffff888013ff5016 by task exploit/141\n  Call Trace:\n   ...\n   kasan_report (mm/kasan/report.c:595)\n   ip6_frag_next (net/ipv6/ip6_output.c:857)\n   br_ip6_fragment (net/ipv6/netfilter.c:212)\n   nf_ct_bridge_post (net/bridge/netfilter/nf_conntrack_bridge.c:407)\n   nf_hook_slow (net/netfilter/core.c:619)\n   br_forward_finish (net/bridge/br_forward.c:66)\n   __br_forward (net/bridge/br_forward.c:115)\n   maybe_deliver (net/bridge/br_forward.c:191)\n   br_flood (net/bridge/br_forward.c:245)\n   br_handle_frame_finish (net/bridge/br_input.c:229)\n   br_handle_frame (net/bridge/br_input.c:442)\n   ...\n   packet_sendmsg (net/packet/af_packet.c:3114)\n   ...\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n  Kernel panic - not syncing: Fatal exception in interrupt",
  "id": "GHSA-435j-q3ff-8922",
  "modified": "2026-07-27T21:31:27Z",
  "published": "2026-07-27T21:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64554"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/00c06ef8c018493943891a7d0ca82b71b24f3180"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1c4f67c89fd27c4df4c70b135c2c59627698b3c0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2731efa6364e47934c96eb69e01ea131e8af8030"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4ac981a8b7ce7aec99a52d08f8a8953e8e120067"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/86f3ce81dd2b4b0aa2c3016c989a943e4b1b643d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8c10778ec674b67a07ea042fcba64270f3f38a5a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c141f69d0a0fb16964dbc293650047e69bda8af7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f2e6596d10783557aeb9668da2a3b4d19deb2001"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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