Linux Distros Unpatched Vulnerability : CVE-2026-45866

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(317273);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/27");

  script_cve_id("CVE-2026-45866");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-45866");

  script_set_attribute(attribute:"synopsis", value:
"The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be
patched.");
  script_set_attribute(attribute:"description", value:
"The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied
patch available.

  - serial: caif: fix use-after-free in caif_serial ldisc_close() There is a use-after-free bug in caif_serial
    where handle_tx() may access ser->tty after the tty has been freed. The race condition occurs between
    ldisc_close() and packet transmission: CPU 0 (close) CPU 1 (xmit) ------------- ------------ ldisc_close()
    tty_kref_put(ser->tty) [tty may be freed here] <-- race window --> caif_xmit() handle_tx() tty = ser->tty
    // dangling ptr tty->ops->write() // UAF! schedule_work() ser_release() unregister_netdevice() The root
    cause is that tty_kref_put() is called in ldisc_close() while the network device is still active and can
    receive packets. Since ser and tty have a 1:1 binding relationship with consistent lifecycles (ser is
    allocated in ldisc_open and freed in ser_release via unregister_netdevice, and each ser binds exactly one
    tty), we can safely defer the tty reference release to ser_release() where the network device is
    unregistered. Fix this by moving tty_kref_put() from ldisc_close() to ser_release(), after
    unregister_netdevice(). This ensures the tty reference is held as long as the network device exists,
    preventing the UAF. Note: We save ser->tty before unregister_netdevice() because ser is embedded in
    netdev's private data and will be freed along with netdev (needs_free_netdev = true). How to reproduce:
    Add mdelay(500) at the beginning of ldisc_close() to widen the race window, then run the reproducer
    program [1]. Note: There is a separate deadloop issue in handle_tx() when using PORT_UNKNOWN serial ports
    (e.g., /dev/ttyS3 in QEMU without proper serial backend). This deadloop exists even without this patch,
    and is likely caused by inconsistency between uart_write_room() and uart_write() in serial core. It has
    been addressed in a separate patch [2]. KASAN report:
    ================================================================== BUG: KASAN: slab-use-after-free in
    handle_tx+0x5d1/0x620 Read of size 1 at addr ffff8881131e1490 by task caif_uaf_trigge/9929 Call Trace:
    <TASK> dump_stack_lvl+0x10e/0x1f0 print_report+0xd0/0x630 kasan_report+0xe4/0x120 handle_tx+0x5d1/0x620
    dev_hard_start_xmit+0x9d/0x6c0 __dev_queue_xmit+0x6e2/0x4410 packet_xmit+0x243/0x360
    packet_sendmsg+0x26cf/0x5500 __sys_sendto+0x4a3/0x520 __x64_sys_sendto+0xe0/0x1c0 do_syscall_64+0xc9/0xf80
    entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f615df2c0d7 Allocated by task 9930: Freed by task
    64: Last potentially related work creation: The buggy address belongs to the object at ffff8881131e1000
    which belongs to the cache kmalloc-cg-2k of size 2048 The buggy address is located 1168 bytes inside of
    freed 2048-byte region [ffff8881131e1000, ffff8881131e1800) The buggy address belongs to the physical
    page: page_owner tracks the page as allocated page last free pid 9778 tgid 9778 stack trace: Memory state
    around the buggy address: ffff8881131e1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8881131e1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881131e1480: fb fb fb fb fb fb fb
    fb fb fb fb fb fb fb fb fb ^ ffff8881131e1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8881131e1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ================================================================== [1]:
    https://gist.github.com/mrpre/f683f244544f7b11e7fa87df9e6c2eeb [2]: https://lore.kernel.org/linux-
    serial/[email protected]/T/#u (CVE-2026-45866)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-45866");
  script_set_attribute(attribute:"solution", value:
"There is no known solution at this time.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-45866");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/05/27");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/05/27");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:linux");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl", "set_linux_os_id.nasl");
  script_require_keys("Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched", "Host/OS/identifier");
  script_require_ports("Host/OS/Debian Linux-11");

  exit(0);
}

if (!get_kb_item("global_settings/vendor_unpatched")) exit(0, "Unpatched Vulnerabilities Detection not active.");
if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (empty_or_null(get_one_kb_item("Host/Debian/dpkg-l"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Debian Linux-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "pkgs": [
          {"reference": "bpftool"},
          {"reference": "btrfs-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "cdrom-core-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "hyperv-daemons"},
          {"reference": "kernel-image-5.10.0-32-alpha-generic-di"},
          {"reference": "libcpupower-dev"},
          {"reference": "libcpupower1"},
          {"reference": "linux-bootwrapper-5.10.0"},
          {"reference": "linux-config-5.10"},
          {"reference": "linux-cpupower"},
          {"reference": "linux-doc"},
          {"reference": "linux-doc-5.10"},
          {"reference": "linux-headers-5.10.0"},
          {"reference": "linux-kbuild-5.10"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-perf"},
          {"reference": "linux-perf-5.10"},
          {"reference": "linux-source"},
          {"reference": "linux-source-5.10"},
          {"reference": "linux-support-5.10.0"},
          {"reference": "loop-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "nic-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "nic-shared-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "nic-wireless-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "pata-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "ppp-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "scsi-core-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "scsi-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "scsi-nic-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "serial-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "usb-serial-modules-5.10.0-32-alpha-generic-di"},
          {"reference": "usbip"}
        ]
      }
    ]
  }
};

var distro_constraints_values = linux_unpatched::get_distro_constraints(distro_constraints_arr:distro_constraints_array);
if (empty_or_null(distro_constraints_values)) audit(AUDIT_HOST_NOT, 'affected');
var report = linux_unpatched::check_unpatched_constraints(distro_constraints_values:distro_constraints_values);

if (!empty_or_null(report))
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}