CVE-2026-74625 (GCVE-0-2026-74625)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-25 05:40
VLAI
Title
netfilter: bridge: release template ct on non-IP path
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: release template ct on non-IP path A bridge nftables ct zone set rule can attach a conntrack template to an skb before nf_ct_bridge_pre() sees it. For non-IPv4 and non-IPv6 EtherTypes, nf_ct_bridge_pre() currently overwrites skb->_nfct with IP_CT_UNTRACKED without releasing the existing template reference. That makes the per-cpu template, and any temporary templates allocated for concurrent use, unreachable and leaks memory until the host runs out of slab. Reset the skb conntrack state before marking the frame untracked so the existing template reference is dropped on the non-IP path.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 3c171f496ef57774f8e5d509923372549734877f , < fc90df37540627d092af770215fb4b7befe9409b (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < daa6e070f8e1e7a4dddec8b64ca37663f8cda917 (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < bd7b16494dacf87e9336a1dcfdada83b9e40edd6 (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < 6ea88401e10e04e0b3bb7a7adea54932fb60b93b (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < 46d559f00b1ab1d114f92d2f16c5ef0093b3b9dd (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < c58d34fe8b7e47bb0b350a7625023b1261342be5 (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < 7cff440d702616022769f2643168d7f9820547a0 (git)
Affected: 3c171f496ef57774f8e5d509923372549734877f , < d45cc8020d7c0a9f01dee42ff5c40bc14c9af72f (git)
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Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 5.10.265 , ≤ 5.10.* (semver)
Unaffected: 5.15.216 , ≤ 5.15.* (semver)
Unaffected: 6.1.183 , ≤ 6.1.* (semver)
Unaffected: 6.6.152 , ≤ 6.6.* (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: bridge: release template ct on non-IP path\n\nA bridge nftables ct zone set rule can attach a conntrack template to\nan skb before nf_ct_bridge_pre() sees it. For non-IPv4 and non-IPv6\nEtherTypes, nf_ct_bridge_pre() currently overwrites skb-\u003e_nfct with\nIP_CT_UNTRACKED without releasing the existing template reference.\n\nThat makes the per-cpu template, and any temporary templates allocated\nfor concurrent use, unreachable and leaks memory until the host runs out\nof slab.\n\nReset the skb conntrack state before marking the frame untracked so the\nexisting template reference is dropped on the non-IP path."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - Non-IP L2 frames (ARP/LLDP) injected into a Linux bridge reach NF_BR_PRE_ROUTING via br_handle_frame\u2192nf_hook_bridge_pre; on overlay/container hosts (VXLAN/GRE bridges in Docker/k8s/OpenStack) remote peers can deliver those frames across routed networks to the victim bridge port.\nAC:L - Once a bridge nftables ct zone set rule runs before NF_IP_PRI_CONNTRACK (-200), every non-IPv4/IPv6 EtherType frame deterministically leaks template references; the attacker controls rule priority, zone value, and can flood ARP/LLDP to accelerate the leak without races.\nPR:N - On bridge firewalls/routers with deployed nftables ct zone marking, exploitation needs only unauthenticated L2 packet delivery\u2014no host UID, capability, or namespace privilege; CAP_NET_ADMIN (obtainable via user namespaces) is an alternate Low path for self-setup but not required on pre-configured appliances.\nUI:N - Bridge netfilter processes received frames automatically in softirq; no victim mount, click, or administrative action is required beyond normal bridge forwarding of attacker-supplied non-IP traffic.\nS:U - Impact is unbounded kernel slab consumption from leaked nf_conn template objects within the host kernel; it does not cross VM, container, IOMMU, or hypervisor security boundaries.\nC:N - The bug is a missing nf_conntrack_put()\u2014a reference-count leak\u2014not a use-after-free, out-of-bounds read, or disclosure primitive; orphaned templates are unreachable and their contents are never returned to the attacker.\nI:N - Only template reference counts are leaked via skb-\u003e_nfct overwrite; no heap corruption, type confusion, or attacker-controlled writes occur, so integrity cannot be compromised beyond availability loss from memory pressure.\nA:H - Each leaked per-CPU and temporary conntrack template is never freed; sustained non-IP frame flooding can exhaust kernel slab until OOM, causing severe host unavailability or panic on memory-allocation failure paths."
            }
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74625",
    "datePublished": "2026-08-22T15:32:07.929Z",
    "dateReserved": "2026-08-15T05:44:03.921Z",
    "dateUpdated": "2026-08-25T05:40:48.341Z",
    "state": "PUBLISHED"
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      "date": "2026-08-29",
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      "cve": "CVE-2026-74625",
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      "version": "2"
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For non-IPv4 and non-IPv6\\nEtherTypes, nf_ct_bridge_pre() currently overwrites skb-\u003e_nfct with\\nIP_CT_UNTRACKED without releasing the existing template reference.\\n\\nThat makes the per-cpu template, and any temporary templates allocated\\nfor concurrent use, unreachable and leaks memory until the host runs out\\nof slab.\\n\\nReset the skb conntrack state before marking the frame untracked so the\\nexisting template reference is dropped on the non-IP 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-25T08:51:23+00:00",
      "cve": "CVE-2026-74625",
      "id": "CVE-2026-74625",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: bridge: release template ct on non-IP path",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74625.json",
      "version": "3"
    }
  }
}



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