Linux Distros Unpatched Vulnerability : CVE-2026-26955

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

include('compat.inc');

if (description)
{
  script_id(299994);
  script_version("1.8");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/16");

  script_cve_id("CVE-2026-26955");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-26955");

  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 is a free implementation of the Remote Desktop Protocol. Prior to version 3.23.0, a malicious RDP
    server can trigger a heap buffer overflow in FreeRDP clients using the GDI surface pipeline (e.g.,
    `xfreerdp`) by sending an RDPGFX ClearCodec surface command with an out-of-bounds destination rectangle.
    The `gdi_SurfaceCommand_ClearCodec()` handler does not call `is_within_surface()` to validate the command
    rectangle against the destination surface dimensions, allowing attacker-controlled `cmd->left`/`cmd->top`
    (and subcodec rectangle offsets) to reach image copy routines that write into `surface->data` without
    bounds enforcement. The OOB write corrupts an adjacent `gdiGfxSurface` struct's `codecs*` pointer with
    attacker-controlled pixel data, and corruption of `codecs*` is sufficient to reach an indirect function
    pointer call (`NSC_CONTEXT.decode` at `nsc.c:500`) on a subsequent codec command  full instruction
    pointer (RIP) control demonstrated in exploitability harness. Users should upgrade to version 3.23.0 to
    receive a patch. (CVE-2026-26955)

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-2026-26955");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-26955");
  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:M/Au:S/C:P/I:P/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:R/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-26955");

  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:"plugin_publication_date", value:"2026/02/26");

  script_set_attribute(attribute:"plugin_type", value:"local");
  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:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:22.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:24.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:freerdp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:freerdp2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:freerdp2");
  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", "Host/OS/Debian Linux-12", "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 = {
  "Debian Linux-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "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-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"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "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"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "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"}
        ]
      }
    ]
  },
  "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"},
          {"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"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "freerdp2"}
        ]
      }
    ]
  }
};

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');
}