CVE-2026-64554 (GCVE-0-2026-64554)

Vulnerability from cvelistv5 – Published: 2026-07-27 20:10 – Updated: 2026-07-27 20:10
VLAI
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
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < 8c10778ec674b67a07ea042fcba64270f3f38a5a (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < 2731efa6364e47934c96eb69e01ea131e8af8030 (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < 00c06ef8c018493943891a7d0ca82b71b24f3180 (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < c141f69d0a0fb16964dbc293650047e69bda8af7 (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < f2e6596d10783557aeb9668da2a3b4d19deb2001 (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < 1c4f67c89fd27c4df4c70b135c2c59627698b3c0 (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < 4ac981a8b7ce7aec99a52d08f8a8953e8e120067 (git)
Affected: 764dd163ac922f8683b5bcd3007251ce7b26cd33 , < 86f3ce81dd2b4b0aa2c3016c989a943e4b1b643d (git)
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Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc4 , ≤ * (original_commit_for_fix)
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      "descriptions": [
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          "lang": "en",
          "value": "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"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-27T20:10:41.726Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/2731efa6364e47934c96eb69e01ea131e8af8030"
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        {
          "url": "https://git.kernel.org/stable/c/86f3ce81dd2b4b0aa2c3016c989a943e4b1b643d"
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      ],
      "title": "netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment()",
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    "datePublished": "2026-07-27T20:10:41.726Z",
    "dateReserved": "2026-07-19T15:36:31.796Z",
    "dateUpdated": "2026-07-27T20:10:41.726Z",
    "state": "PUBLISHED"
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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 - 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  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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Detection rules are retrieved from Rulezet.