Linux Distros Unpatched Vulnerability : CVE-2026-72166

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

include('compat.inc');

if (description)
{
  script_id(335631);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/15");

  script_cve_id("CVE-2026-72166");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-72166");

  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.

  - net/9p: fix infinite loop in p9_client_rpc on fatal signal When p9_client_rpc() is called with type
    P9_TFLUSH and the transport has no peer (e.g. fd transport backed by pipes with no 9p server), a fatal
    signal causes an infinite loop: again: err = io_wait_event_killable(req->wq, ...) /* SIGKILL wakes the
    task, returns -ERESTARTSYS */ if (err == -ERESTARTSYS && c->status == Connected && type == P9_TFLUSH) {
    sigpending = 1; clear_thread_flag(TIF_SIGPENDING); goto again; } clear_thread_flag() clears TIF_SIGPENDING
    before jumping back to io_wait_event_killable(). signal_pending_state() checks TIF_SIGPENDING, finds it
    zero, and the task goes to sleep again. The task can only wake on the next signal delivery that calls
    signal_wake_up() and sets TIF_SIGPENDING again. When that happens the loop repeats, clears TIF_SIGPENDING,
    and sleeps again indefinitely. This is triggered in practice by coredump_wait(): when a thread in a multi-
    threaded process causes a coredump (e.g. via SIGSYS from Syscall User Dispatch), coredump_wait() sends
    SIGKILL to all other threads and waits for them to call mm_release(). If one of those threads is blocked
    in p9_client_rpc() over an fd transport with no peer, it enters the P9_TFLUSH loop and never calls
    mm_release(), so coredump_wait() stalls forever: INFO: task syz.0.18:676 blocked for more than 143
    seconds. Not tainted 6.12.77+ #1 task:syz.0.18 state:D stack:27600 pid:676 tgid:673 ppid:630
    flags:0x00000004 Call Trace: <TASK> context_switch kernel/sched/core.c:5344 [inline]
    __schedule+0xcb4/0x5d50 kernel/sched/core.c:6724 __schedule_loop kernel/sched/core.c:6801 [inline]
    schedule+0xe5/0x350 kernel/sched/core.c:6816 schedule_timeout+0x253/0x290 kernel/time/timer.c:2593
    do_wait_for_common kernel/sched/completion.c:95 [inline] __wait_for_common+0x409/0x600
    kernel/sched/completion.c:116 wait_for_common kernel/sched/completion.c:127 [inline]
    wait_for_completion_state+0x1d/0x40 kernel/sched/completion.c:264 coredump_wait fs/coredump.c:448 [inline]
    do_coredump+0x854/0x4350 fs/coredump.c:629 get_signal+0x1425/0x2730 kernel/signal.c:2903
    arch_do_signal_or_restart+0x81/0x880 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop
    kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
    __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0xf9/0x160
    kernel/entry/common.c:218 do_syscall_64+0x102/0x220 arch/x86/entry/common.c:84
    entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> Fix: check fatal_signal_pending() before clearing
    TIF_SIGPENDING in the P9_TFLUSH retry loop. At that point TIF_SIGPENDING is still set, so
    fatal_signal_pending() works correctly. If a fatal signal is pending, jump to recalc_sigpending to restore
    TIF_SIGPENDING and return -ERESTARTSYS to the caller. The same defect is present in stable kernels back to
    5.4. On those kernels the infinite loop is broken earlier by a second SIGKILL from the parent process
    (e.g. kill_and_wait() retrying after a timeout), resulting in a zombie process and a shutdown delay rather
    than a permanent D-state hang, but the underlying flaw is the same. Found by Linux Verification Center
    (linuxtesting.org) with Syzkaller. (CVE-2026-72166)

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-2026-72166");
  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-2026-72166");

  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:"2026/08/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/15");

  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 third_party_support = get_kb_item('Host/OS/extended-third-party');
if (!empty_or_null(third_party_support)) {
    var third_party_vendors = distro_constraints_values['third_party'];
    if (!empty_or_null(third_party_vendors)) {
        var vendor;
        foreach vendor (third_party_vendors) {
            if (vendor == third_party_support) exit(0, 'A third party management patch is available for this vulnerability from ' + vendor + '.\n');
        }
    }
}

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');
}