{
  "cveId": "CVE-2021-4454",
  "url": "https://patchblox.com/security/cve/CVE-2021-4454",
  "summary": "CVE-2021-4454 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-4454, released March 27, 2025. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  can: j1939: fix errant WARN_ON_ONCE in j1939_ses...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate  The conclusion \u0022j1939_session_deactivate() should be called with a session ref-count of at least 2\u0022 is incorrect. In some concurrent scenarios, j1939_session_deactivate can be called with the session ref-count less than 2. But there is not any problem because it will check the session active state before session putting in j1939_session_deactivate_locked().  Here is the concurrent scenario of the problem reported by syzbot and my reproduction log.          cpu0                            cpu1                                 j1939_xtp_rx_eoma j1939_xtp_rx_abort_one                                 j1939_session_get_by_addr [kref == 2] j1939_session_get_by_addr [kref == 3] j1939_session_deactivate [kref == 2] j1939_session_put [kref == 1] \t\t\t\tj1939_session_completed \t\t\t\tj1939_session_deactivate \t\t\t\tWARN_ON_ONCE(kref \u003C 2)  ===================================================== WARNING: CPU: 1 PID: 21 at net/can/j1939/transport.c:1088 j1939_session_deactivate\u002B0x5f/0x70 CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 5.14.0-rc7\u002B #32 Hardware name: QEMU Standard PC (i440FX \u002B PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014 RIP: 0010:j1939_session_deactivate\u002B0x5f/0x70 Call Trace:  j1939_session_deactivate_activate_next\u002B0x11/0x28  j1939_xtp_rx_eoma\u002B0x12a/0x180  j1939_tp_recv\u002B0x4a2/0x510  j1939_can_recv\u002B0x226/0x380  can_rcv_filter\u002B0xf8/0x220  can_receive\u002B0x102/0x220  ? process_backlog\u002B0xf0/0x2c0  can_rcv\u002B0x53/0xf0  __netif_receive_skb_one_core\u002B0x67/0x90  ? process_backlog\u002B0x97/0x2c0  __netif_receive_skb\u002B0x22/0x80",
  "published": "2025-03-27T17:15:35Z",
  "severity": "medium",
  "cvss": 5.5,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.00591,
  "epssPercentile": 0.4848,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "6.1.11-1",
      "fix": "DEBIAN-CVE-2021-4454",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-4454",
      "released": "2025-03-27T17:15:35Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.1.11-1",
      "fix": "DEBIAN-CVE-2021-4454",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-4454",
      "released": "2025-03-27T17:15:35Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "6.1.11-1",
      "fix": "DEBIAN-CVE-2021-4454",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-4454",
      "released": "2025-03-27T17:15:35Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T00:53:09Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}