GHSA-98RV-7H6M-5Q72

Vulnerability from github – Published: 2026-08-15 15:30 – Updated: 2026-08-17 06:33
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

net: bridge: stop fast-leave after deleting a port group

br_multicast_leave_group() iterates mp->ports with pp = &p->next in its fast-leave path. After br_multicast_del_pg() removes p, continuing the loop advances pp through the deleted entry.

If multicast-to-unicast was enabled, the bridge can hold multiple port groups for the same port and group with different source MAC addresses. Once multicast-to-unicast is disabled, br_port_group_equal() matches those entries by port only. A fast leave can then delete one entry and continue from its stale next pointer, leaving mp->ports pointing at a deleted port group.

Fast leave only needs to remove one matching port group. Break after br_multicast_del_pg() so the loop stops before dereferencing the removed entry.

Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-74480"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T13:17:52Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: stop fast-leave after deleting a port group\n\nbr_multicast_leave_group() iterates mp-\u003eports with pp = \u0026p-\u003enext in\nits fast-leave path. After br_multicast_del_pg() removes p,\ncontinuing the loop advances pp through the deleted entry.\n\nIf multicast-to-unicast was enabled, the bridge can hold multiple port\ngroups for the same port and group with different source MAC\naddresses. Once multicast-to-unicast is disabled,\nbr_port_group_equal() matches those entries by port only. A fast leave\ncan then delete one entry and continue from its stale next pointer,\nleaving mp-\u003eports pointing at a deleted port group.\n\nFast leave only needs to remove one matching port group. Break after\nbr_multicast_del_pg() so the loop stops before dereferencing the\nremoved entry.",
  "id": "GHSA-98rv-7h6m-5q72",
  "modified": "2026-08-17T06:33:49Z",
  "published": "2026-08-15T15:30:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74480"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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