Vulnerability-Lookup

GHSA-VJWV-39Q4-JXGJ

Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31

Details

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74625"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T16:16:35Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-vjwv-39q4-jxgj",
  "modified": "2026-08-25T06:31:23Z",
  "published": "2026-08-22T18:30:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74625"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/46d559f00b1ab1d114f92d2f16c5ef0093b3b9dd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6ea88401e10e04e0b3bb7a7adea54932fb60b93b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7cff440d702616022769f2643168d7f9820547a0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bd7b16494dacf87e9336a1dcfdada83b9e40edd6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c58d34fe8b7e47bb0b350a7625023b1261342be5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d45cc8020d7c0a9f01dee42ff5c40bc14c9af72f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/daa6e070f8e1e7a4dddec8b64ca37663f8cda917"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fc90df37540627d092af770215fb4b7befe9409b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-25 05:40

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

Linux mitre root

References

8 references

URL	Tags
https://git.kernel.org/stable/c/fc90df37540627d09…
https://git.kernel.org/stable/c/daa6e070f8e1e7a4d…
https://git.kernel.org/stable/c/bd7b16494dacf87e9…
https://git.kernel.org/stable/c/6ea88401e10e04e0b…
https://git.kernel.org/stable/c/46d559f00b1ab1d11…
https://git.kernel.org/stable/c/c58d34fe8b7e47bb0…
https://git.kernel.org/stable/c/7cff440d702616022…
https://git.kernel.org/stable/c/d45cc8020d7c0a9f0…

Impacted products

2 products

Vendor	Product	Version
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)
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)

Show details on NVD website

JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/bridge/netfilter/nf_conntrack_bridge.c"
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              "version": "5.3"
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              "version": "0",
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              "status": "unaffected",
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              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
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            {
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              "status": "unaffected",
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        {
          "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",
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            {
              "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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      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T05:40:48.341Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        {
          "url": "https://git.kernel.org/stable/c/d45cc8020d7c0a9f01dee42ff5c40bc14c9af72f"
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      "title": "netfilter: bridge: release template ct on non-IP path",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "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"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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