Linux Distros Unpatched Vulnerability : CVE-2025-21897

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

include('compat.inc');

if (description)
{
  script_id(250071);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/08/15");

  script_cve_id("CVE-2025-21897");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2025-21897");

  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.

  - In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix pick_task_scx() picking
    non-queued tasks when it's called without balance() a6250aa251ea (sched_ext: Handle cases where
    pick_task_scx() is called without preceding balance_scx()) added a workaround to handle the cases where
    pick_task_scx() is called without prececing balance_scx() which is due to a fair class bug where
    pick_taks_fair() may return NULL after a true return from balance_fair(). The workaround detects when
    pick_task_scx() is called without preceding balance_scx() and emulates SCX_RQ_BAL_KEEP and triggers
    kicking to avoid stalling. Unfortunately, the workaround code was testing whether @prev was on SCX to
    decide whether to keep the task running. This is incorrect as the task may be on SCX but no longer
    runnable. This could lead to a non-runnable task to be returned from pick_task_scx() which cause
    interesting confusions and failures. e.g. A common failure mode is the task ending up with (!on_rq &&
    on_cpu) state which can cause potential wakers to busy loop, which can easily lead to deadlocks. Fix it by
    testing whether @prev has SCX_TASK_QUEUED set. This makes @prev_on_scx only used in one place. Open code
    the usage and improve the comment while at it. (CVE-2025-21897)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2025-21897");
  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:L/AC:L/Au:N/C:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2025-21897");

  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:"2025/04/01");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/08/15");

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

  script_copyright(english:"This script is Copyright (C) 2025 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/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04", "Host/OS/Ubuntu Linux-24.04");

  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 = {
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "linux-hwe-edge"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "linux-aws-5.0"},
          {"reference": "linux-aws-5.3"},
          {"reference": "linux-azure-5.3"},
          {"reference": "linux-azure-cloud-tools-4.15.0"},
          {"reference": "linux-azure-edge"},
          {"reference": "linux-azure-headers-4.15.0"},
          {"reference": "linux-azure-tools-4.15.0"},
          {"reference": "linux-cloud-tools-4.15.0"},
          {"reference": "linux-gcp-5.3"},
          {"reference": "linux-gcp-headers-4.15.0"},
          {"reference": "linux-gcp-tools-4.15.0"},
          {"reference": "linux-gke-4.15"},
          {"reference": "linux-gke-5.4"},
          {"reference": "linux-gkeop-5.4"},
          {"reference": "linux-headers-4.15.0"},
          {"reference": "linux-hwe"},
          {"reference": "linux-hwe-edge"},
          {"reference": "linux-image-4.15.0"},
          {"reference": "linux-image-unsigned-4.15.0"},
          {"reference": "linux-modules-4.15.0"},
          {"reference": "linux-modules-extra-4.15.0"},
          {"reference": "linux-oem-headers-4.15.0"},
          {"reference": "linux-oem-tools-4.15.0"},
          {"reference": "linux-oracle-5.0"},
          {"reference": "linux-oracle-5.3"},
          {"reference": "linux-tools-4.15.0"},
          {"reference": "linux-udebs-azure"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "linux-aws-5.11"},
          {"reference": "linux-aws-5.13"},
          {"reference": "linux-aws-5.8"},
          {"reference": "linux-azure-5.11"},
          {"reference": "linux-azure-5.13"},
          {"reference": "linux-azure-5.8"},
          {"reference": "linux-azure-fde"},
          {"reference": "linux-buildinfo-5.4.0"},
          {"reference": "linux-buildinfo-5.6.0"},
          {"reference": "linux-cloud-tools-5.4.0"},
          {"reference": "linux-cloud-tools-5.6.0"},
          {"reference": "linux-gcp-5.11"},
          {"reference": "linux-gcp-5.13"},
          {"reference": "linux-gcp-5.8"},
          {"reference": "linux-gke"},
          {"reference": "linux-gke-5.15"},
          {"reference": "linux-gkeop"},
          {"reference": "linux-gkeop-5.15"},
          {"reference": "linux-headers-5.4.0"},
          {"reference": "linux-headers-5.6.0"},
          {"reference": "linux-hwe-5.11"},
          {"reference": "linux-hwe-5.13"},
          {"reference": "linux-hwe-5.8"},
          {"reference": "linux-image-5.4.0"},
          {"reference": "linux-image-unsigned-5.6.0"},
          {"reference": "linux-intel-5.13"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-modules-5.4.0"},
          {"reference": "linux-modules-5.6.0"},
          {"reference": "linux-modules-extra-5.4.0"},
          {"reference": "linux-modules-extra-5.6.0"},
          {"reference": "linux-oem-5.10"},
          {"reference": "linux-oem-5.13"},
          {"reference": "linux-oem-5.14"},
          {"reference": "linux-oem-5.6-headers-5.6.0"},
          {"reference": "linux-oem-5.6-tools-5.6.0"},
          {"reference": "linux-oem-5.6-tools-common"},
          {"reference": "linux-oem-5.6-tools-host"},
          {"reference": "linux-oracle-5.11"},
          {"reference": "linux-oracle-5.13"},
          {"reference": "linux-oracle-5.8"},
          {"reference": "linux-raspi2"},
          {"reference": "linux-riscv-5.11"},
          {"reference": "linux-riscv-5.8"},
          {"reference": "linux-riscv-headers-5.4.0"},
          {"reference": "linux-riscv-tools-5.4.0"},
          {"reference": "linux-tools-5.4.0"},
          {"reference": "linux-tools-5.6.0"},
          {"reference": "linux-udebs-generic"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "linux-allwinner-5.19"},
          {"reference": "linux-aws-5.19"},
          {"reference": "linux-aws-6.2"},
          {"reference": "linux-aws-6.5"},
          {"reference": "linux-azure-5.19"},
          {"reference": "linux-azure-6.2"},
          {"reference": "linux-azure-6.5"},
          {"reference": "linux-azure-fde-5.19"},
          {"reference": "linux-azure-fde-6.2"},
          {"reference": "linux-buildinfo-5.15.0"},
          {"reference": "linux-buildinfo-5.17.0"},
          {"reference": "linux-cloud-tools-5.15.0"},
          {"reference": "linux-cloud-tools-5.17.0"},
          {"reference": "linux-gcp-5.19"},
          {"reference": "linux-gcp-6.2"},
          {"reference": "linux-gcp-6.5"},
          {"reference": "linux-headers-5.15.0"},
          {"reference": "linux-headers-5.17.0"},
          {"reference": "linux-hwe-5.19"},
          {"reference": "linux-hwe-6.2"},
          {"reference": "linux-hwe-6.5"},
          {"reference": "linux-image-5.15.0"},
          {"reference": "linux-image-unsigned-5.17.0"},
          {"reference": "linux-intel-iot-realtime"},
          {"reference": "linux-lowlatency-hwe-5.19"},
          {"reference": "linux-lowlatency-hwe-6.2"},
          {"reference": "linux-lowlatency-hwe-6.5"},
          {"reference": "linux-modules-5.15.0"},
          {"reference": "linux-modules-5.17.0"},
          {"reference": "linux-modules-extra-5.15.0"},
          {"reference": "linux-modules-extra-5.17.0"},
          {"reference": "linux-nvidia-6.2"},
          {"reference": "linux-nvidia-6.5"},
          {"reference": "linux-oem-5.17-headers-5.17.0"},
          {"reference": "linux-oem-5.17-tools-5.17.0"},
          {"reference": "linux-oem-5.17-tools-host"},
          {"reference": "linux-oem-6.0"},
          {"reference": "linux-oem-6.1"},
          {"reference": "linux-oem-6.5"},
          {"reference": "linux-oracle-6.5"},
          {"reference": "linux-realtime"},
          {"reference": "linux-riscv-5.19"},
          {"reference": "linux-riscv-6.5"},
          {"reference": "linux-riscv-headers-5.15.0"},
          {"reference": "linux-riscv-tools-5.15.0"},
          {"reference": "linux-starfive-5.19"},
          {"reference": "linux-starfive-6.2"},
          {"reference": "linux-starfive-6.5"},
          {"reference": "linux-tools-5.15.0"},
          {"reference": "linux-tools-5.17.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "linux-raspi-realtime"},
          {"reference": "linux-realtime"}
        ]
      }
    ]
  }
};

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');
}