GHSA-76V9-JPJ5-V4RQ

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33
VLAI
Details

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

tipc: fix UAF in tipc_l2_send_msg()

Syzbot reported a slab-use-after-free in ipvlan_hard_header() when called from tipc_l2_send_msg().

The root cause is that tipc_disable_l2_media() calls synchronize_net() while b->media_ptr is still valid. This allows concurrent RCU readers to obtain the device pointer after synchronize_net() has finished. The pointer is cleared later in bearer_disable(), but without any subsequent synchronization, allowing the device to be freed while still in use by readers.

Fix this by clearing b->media_ptr in tipc_disable_l2_media() before calling synchronize_net().

This is safe to do now because the call order in bearer_disable() was reversed in 0d051bf93c06 ("tipc: make bearer packet filtering generic") to call tipc_node_delete_links() (which needs the pointer) before disable_media().

https: //lore.kernel.org/netdev/6a2c1007.428ffe26.258b27.015d.GAE@google.com/T/#u

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-2026-74255"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:24Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix UAF in tipc_l2_send_msg()\n\nSyzbot reported a slab-use-after-free in ipvlan_hard_header() when\ncalled from tipc_l2_send_msg().\n\nThe root cause is that tipc_disable_l2_media() calls synchronize_net()\nwhile b-\u003emedia_ptr is still valid. This allows concurrent RCU readers\nto obtain the device pointer after synchronize_net() has finished.\nThe pointer is cleared later in bearer_disable(), but without any\nsubsequent synchronization, allowing the device to be freed while\nstill in use by readers.\n\nFix this by clearing b-\u003emedia_ptr in tipc_disable_l2_media() before\ncalling synchronize_net().\n\nThis is safe to do now because the call order in bearer_disable()\nwas reversed in 0d051bf93c06 (\"tipc: make bearer packet filtering generic\")\nto call tipc_node_delete_links() (which needs the pointer) before\ndisable_media().\n\nhttps: //lore.kernel.org/netdev/6a2c1007.428ffe26.258b27.015d.GAE@google.com/T/#u",
  "id": "GHSA-76v9-jpj5-v4rq",
  "modified": "2026-08-17T06:33:34Z",
  "published": "2026-08-15T06:32:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74255"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0d8a12d7143126afdf9fbe2e3d438650dd6603ed"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/35e0297a93c3c34a3924eeef816c03504e3ab5c5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/50ff092633b06382e5091dd5b093ce943d4ac2f9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/609ced2301be1df7e7ed2ef47d1d916674e6ba3b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/71aafa16d79b107b33837f60b6cbc7d0cb8c5708"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/aef12b5ce793dea6b3a97a58fd0f946000ae8945"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f4002f1c669cc02e3763f479fc25ff1dfa9e2420"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f4c3d89fc986b0da196ddfc6cfe0ea5d5d08bec6"
    }
  ],
  "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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