GHSA-WR5R-399Q-PWFR

Vulnerability from github – Published: 2026-10-23 12:31 – Updated: 2026-10-23 12:31
VLAI
Details

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

ksmbd: remove stale channels from all sessions on teardown

ksmbd_sessions_deregister() removes a connection's channels from other sessions' channel lists only while conn->binding is still set:

if (conn->binding) {
    hash_for_each_safe(sessions_table, ...)
        ksmbd_chann_del(conn, sess);
}

conn->binding is a transient flag: it is cleared once a binding SESSION_SETUP completes, and also by a subsequent non-binding SESSION_SETUP on the same connection (a reauthentication on a bound channel, or a new SessionId==0 setup). A connection that has bound a channel into another session's ksmbd_chann_list and then clears conn->binding leaves that channel behind when it disconnects: the channel, whose chann->conn points at the now freed struct ksmbd_conn, stays on the owner session's list.

When the owning connection later tears down, the second loop dereferences the stale channel:

xa_for_each(&sess->ksmbd_chann_list, chann_id, chann)
    if (chann->conn != conn)
        ksmbd_conn_set_exiting(chann->conn);   /* freed */

which is a use-after-free write into the freed ksmbd_conn (the same stale channel is also walked by show_proc_session() through /proc). The session is leaked as well, because its channel list never empties.

Remove the conn->binding gate so a connection always removes its channels from every session on teardown.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98870"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T12:18:20Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: remove stale channels from all sessions on teardown\n\nksmbd_sessions_deregister() removes a connection\u0027s channels from other\nsessions\u0027 channel lists only while conn-\u003ebinding is still set:\n\n\tif (conn-\u003ebinding) {\n\t\thash_for_each_safe(sessions_table, ...)\n\t\t\tksmbd_chann_del(conn, sess);\n\t}\n\nconn-\u003ebinding is a transient flag: it is cleared once a binding\nSESSION_SETUP completes, and also by a subsequent non-binding\nSESSION_SETUP on the same connection (a reauthentication on a bound\nchannel, or a new SessionId==0 setup). A connection that has bound a\nchannel into another session\u0027s ksmbd_chann_list and then clears\nconn-\u003ebinding leaves that channel behind when it disconnects: the\nchannel, whose chann-\u003econn points at the now freed struct ksmbd_conn,\nstays on the owner session\u0027s list.\n\nWhen the owning connection later tears down, the second loop\ndereferences the stale channel:\n\n\txa_for_each(\u0026sess-\u003eksmbd_chann_list, chann_id, chann)\n\t\tif (chann-\u003econn != conn)\n\t\t\tksmbd_conn_set_exiting(chann-\u003econn);   /* freed */\n\nwhich is a use-after-free write into the freed ksmbd_conn (the same\nstale channel is also walked by show_proc_session() through /proc). The\nsession is leaked as well, because its channel list never empties.\n\nRemove the conn-\u003ebinding gate so a connection always removes its\nchannels from every session on teardown.",
  "id": "GHSA-wr5r-399q-pwfr",
  "modified": "2026-10-23T12:31:35Z",
  "published": "2026-10-23T12:31:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98870"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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