CVE-2026-53349 (GCVE-0-2026-53349)
Vulnerability from cvelistv5
Published
2026-07-01 13:32
Modified
2026-07-01 13:32
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack: destroy stale expectfn expectations on unregister NAT helpers such as nf_nat_h323 store a raw pointer to module text in exp->expectfn (e.g. ip_nat_q931_expect). nf_ct_helper_expectfn_unregister() only unlinks the callback descriptor and never walks the expectation table, so an expectation pending at module removal survives with a dangling exp->expectfn into freed module text. When the expected connection arrives, init_conntrack() invokes exp->expectfn(), now a stale pointer into the unloaded module. Reproduced on a KASAN build by loading the H.323 helpers, creating a Q.931 expectation, unloading nf_nat_h323, then connecting to the expected port: Oops: int3: 0000 [#1] SMP KASAN NOPTI RIP: 0010:0xffffffffa06102d1 init_conntrack.isra.0 (net/netfilter/nf_conntrack_core.c:1862) nf_conntrack_in (net/netfilter/nf_conntrack_core.c:2049) ipv4_conntrack_local (net/netfilter/nf_conntrack_proto.c:223) nf_hook_slow (net/netfilter/core.c:619) __ip_local_out (net/ipv4/ip_output.c:120) __tcp_transmit_skb (net/ipv4/tcp_output.c:1715) tcp_connect (net/ipv4/tcp_output.c:4374) tcp_v4_connect (net/ipv4/tcp_ipv4.c:345) __sys_connect (net/socket.c:2167) Modules linked in: nf_conntrack_h323 [last unloaded: nf_nat_h323] Reaching the dangling state requires CAP_SYS_MODULE in the initial user namespace to remove a NAT helper that still has live expectations, so this is a robustness fix; leaving an expectation pointing at freed text is wrong regardless. Add nf_ct_helper_expectfn_destroy(), which walks the expectation table and drops every expectation whose ->expectfn matches the descriptor being torn down. Call it from each NAT helper's exit path after the existing RCU grace period, so no expectation outlives the code it points at and no extra synchronize_rcu() is introduced. With the fix, the same reproducer runs to completion without the Oops.
References
Impacted products
Vendor Product Version
Linux Linux Version: f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4
Version: f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4
Version: f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4
Version: f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4
Version: f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4
Version: f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "include/net/netfilter/nf_conntrack_helper.h",
            "net/ipv4/netfilter/nf_nat_h323.c",
            "net/netfilter/nf_conntrack_helper.c",
            "net/netfilter/nf_nat_core.c",
            "net/netfilter/nf_nat_sip.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "programFiles": [
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            "net/ipv4/netfilter/nf_nat_h323.c",
            "net/netfilter/nf_conntrack_helper.c",
            "net/netfilter/nf_nat_core.c",
            "net/netfilter/nf_nat_sip.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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      ],
      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack: destroy stale expectfn expectations on unregister\n\nNAT helpers such as nf_nat_h323 store a raw pointer to module text in\nexp-\u003eexpectfn (e.g. ip_nat_q931_expect). nf_ct_helper_expectfn_unregister()\nonly unlinks the callback descriptor and never walks the expectation table,\nso an expectation pending at module removal survives with a dangling\nexp-\u003eexpectfn into freed module text.\n\nWhen the expected connection arrives, init_conntrack() invokes\nexp-\u003eexpectfn(), now a stale pointer into the unloaded module. Reproduced\non a KASAN build by loading the H.323 helpers, creating a Q.931\nexpectation, unloading nf_nat_h323, then connecting to the expected port:\n\n Oops: int3: 0000 [#1] SMP KASAN NOPTI\n RIP: 0010:0xffffffffa06102d1\n  init_conntrack.isra.0 (net/netfilter/nf_conntrack_core.c:1862)\n  nf_conntrack_in (net/netfilter/nf_conntrack_core.c:2049)\n  ipv4_conntrack_local (net/netfilter/nf_conntrack_proto.c:223)\n  nf_hook_slow (net/netfilter/core.c:619)\n  __ip_local_out (net/ipv4/ip_output.c:120)\n  __tcp_transmit_skb (net/ipv4/tcp_output.c:1715)\n  tcp_connect (net/ipv4/tcp_output.c:4374)\n  tcp_v4_connect (net/ipv4/tcp_ipv4.c:345)\n  __sys_connect (net/socket.c:2167)\n Modules linked in: nf_conntrack_h323 [last unloaded: nf_nat_h323]\n\nReaching the dangling state requires CAP_SYS_MODULE in the initial user\nnamespace to remove a NAT helper that still has live expectations, so this\nis a robustness fix; leaving an expectation pointing at freed text is wrong\nregardless.\n\nAdd nf_ct_helper_expectfn_destroy(), which walks the expectation table and\ndrops every expectation whose -\u003eexpectfn matches the descriptor being torn\ndown. Call it from each NAT helper\u0027s exit path after the existing RCU grace\nperiod, so no expectation outlives the code it points at and no extra\nsynchronize_rcu() is introduced. With the fix, the same reproducer runs to\ncompletion without the Oops."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-01T13:32:27.412Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/fbfde85308b99938a6092c48753214d190ece48d"
        },
        {
          "url": "https://git.kernel.org/stable/c/29d8cc44bbdf7b83a1929912214afe6643c1b4f1"
        },
        {
          "url": "https://git.kernel.org/stable/c/f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d"
        },
        {
          "url": "https://git.kernel.org/stable/c/9d017671dcfcec23321fb7962dea624f9e71ddb1"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf8c0b5dd203be94c2ad50e264cec19267c6bd39"
        },
        {
          "url": "https://git.kernel.org/stable/c/c3009418f9fa1dcb3eb86f4d8c92583537b5faa3"
        }
      ],
      "title": "netfilter: nf_conntrack: destroy stale expectfn expectations on unregister",
      "x_generator": {
        "engine": "bippy-1.2.0"
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53349",
    "datePublished": "2026-07-01T13:32:27.412Z",
    "dateReserved": "2026-06-09T07:44:35.399Z",
    "dateUpdated": "2026-07-01T13:32:27.412Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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