Linux Distros Unpatched Vulnerability : CVE-2026-121956

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

include('compat.inc');

if (description)
{
  script_id(376217);
  script_version("1.4");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/11/06");

  script_cve_id("CVE-2026-121956");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-121956");

  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.

  - FreeRDP before 3.32.2 contains a double free in the WinPR Kerberos SSPI retrieveSomeTgt function, which
    installs the krb5 default realm into a target principal that has an empty realm without taking ownership
    of it. Unauthenticated remote clients can send a crafted NLA/CredSSP u2u TGT request whose server-name
    component contains '@' to corrupt the heap and crash the server process. (CVE-2026-121956)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://access.redhat.com/security/cve/cve-2026-121956");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-121956");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-121956");
  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:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:U/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:P");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-121956");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/11/04");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/11/05");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:redhat:enterprise_linux:10");
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  script_set_attribute(attribute:"cpe", value:"cpe:/a:redhat:enterprise_linux:9");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:centos:centos:8");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:13.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:8");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:9");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:freerdp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:freerdp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:freerdp-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:freerdp-libs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:libwinpr");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:libwinpr-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:freerdp2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:freerdp3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:freerdp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:freerdp-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:freerdp-libs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:libwinpr");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:libwinpr-devel");
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  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/CentOS Linux-8", "Host/OS/Debian Linux-12", "Host/OS/Debian Linux-13", "Host/OS/Red Hat Enterprise Linux-10", "Host/OS/Red Hat Enterprise Linux-8", "Host/OS/Red Hat Enterprise Linux-9", "Host/OS/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04");

  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/CentOS/rpm-list")) && empty_or_null(get_one_kb_item("Host/Debian/dpkg-l")) && empty_or_null(get_one_kb_item("Host/RedHat/rpm-list"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "freerdp2-dev"},
          {"reference": "freerdp2-shadow-x11"},
          {"reference": "freerdp2-wayland"},
          {"reference": "freerdp2-x11"},
          {"reference": "libfreerdp-client2-2"},
          {"reference": "libfreerdp-server2-2"},
          {"reference": "libfreerdp-shadow-subsystem2-2"},
          {"reference": "libfreerdp-shadow2-2"},
          {"reference": "libfreerdp2-2"},
          {"reference": "libuwac0-0"},
          {"reference": "libuwac0-dev"},
          {"reference": "libwinpr-tools2-2"},
          {"reference": "libwinpr2-2"},
          {"reference": "libwinpr2-dev"},
          {"reference": "winpr-utils"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "freerdp3-dev"},
          {"reference": "freerdp3-proxy"},
          {"reference": "freerdp3-proxy-modules"},
          {"reference": "freerdp3-sdl"},
          {"reference": "freerdp3-shadow-x11"},
          {"reference": "freerdp3-wayland"},
          {"reference": "freerdp3-x11"},
          {"reference": "libfreerdp-client3-3"},
          {"reference": "libfreerdp-server-proxy3-3"},
          {"reference": "libfreerdp-server3-3"},
          {"reference": "libfreerdp-shadow-subsystem3-3"},
          {"reference": "libfreerdp-shadow3-3"},
          {"reference": "libfreerdp3-3"},
          {"reference": "libwinpr-tools3-3"},
          {"reference": "libwinpr3-3"},
          {"reference": "libwinpr3-dev"},
          {"reference": "winpr3-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "freerdp-x11"},
          {"reference": "freerdp-x11-dbg"},
          {"reference": "libfreerdp-cache1.1"},
          {"reference": "libfreerdp-client1.1"},
          {"reference": "libfreerdp-codec1.1"},
          {"reference": "libfreerdp-common1.1.0"},
          {"reference": "libfreerdp-core1.1"},
          {"reference": "libfreerdp-crypto1.1"},
          {"reference": "libfreerdp-dev"},
          {"reference": "libfreerdp-gdi1.1"},
          {"reference": "libfreerdp-locale1.1"},
          {"reference": "libfreerdp-plugins-standard"},
          {"reference": "libfreerdp-primitives1.1"},
          {"reference": "libfreerdp-rail1.1"},
          {"reference": "libfreerdp-utils1.1"},
          {"reference": "libwinpr-asn1-0.1"},
          {"reference": "libwinpr-bcrypt0.1"},
          {"reference": "libwinpr-credentials0.1"},
          {"reference": "libwinpr-credui0.1"},
          {"reference": "libwinpr-crt0.1"},
          {"reference": "libwinpr-crypto0.1"},
          {"reference": "libwinpr-dev"},
          {"reference": "libwinpr-dsparse0.1"},
          {"reference": "libwinpr-environment0.1"},
          {"reference": "libwinpr-error0.1"},
          {"reference": "libwinpr-file0.1"},
          {"reference": "libwinpr-handle0.1"},
          {"reference": "libwinpr-heap0.1"},
          {"reference": "libwinpr-input0.1"},
          {"reference": "libwinpr-interlocked0.1"},
          {"reference": "libwinpr-io0.1"},
          {"reference": "libwinpr-library0.1"},
          {"reference": "libwinpr-path0.1"},
          {"reference": "libwinpr-pipe0.1"},
          {"reference": "libwinpr-pool0.1"},
          {"reference": "libwinpr-registry0.1"},
          {"reference": "libwinpr-rpc0.1"},
          {"reference": "libwinpr-sspi0.1"},
          {"reference": "libwinpr-sspicli0.1"},
          {"reference": "libwinpr-synch0.1"},
          {"reference": "libwinpr-sysinfo0.1"},
          {"reference": "libwinpr-thread0.1"},
          {"reference": "libwinpr-timezone0.1"},
          {"reference": "libwinpr-utils0.1"},
          {"reference": "libwinpr-winhttp0.1"},
          {"reference": "libwinpr-winsock0.1"},
          {"reference": "libxfreerdp-client-dbg"},
          {"reference": "libxfreerdp-client1.1"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "freerdp"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-10": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "10",
        "pkgs": [
          {"reference": "freerdp"}
        ]
      }
    ]
  },
  "CentOS Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "freerdp"},
          {"reference": "freerdp-devel"},
          {"reference": "freerdp-libs"},
          {"reference": "libwinpr"},
          {"reference": "libwinpr-devel"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "freerdp"},
          {"reference": "freerdp-devel"},
          {"reference": "freerdp-libs"},
          {"reference": "libwinpr"},
          {"reference": "libwinpr-devel"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-9": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "9",
        "pkgs": [
          {"reference": "freerdp"},
          {"reference": "freerdp-devel"},
          {"reference": "freerdp-libs"},
          {"reference": "libwinpr"},
          {"reference": "libwinpr-devel"}
        ]
      }
    ]
  }
};

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');
}