Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : LibVNCServer vulnerabilities (USN-8463-1)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-8463-1. The text
# itself is copyright (C) Canonical, Inc. See
# <https://ubuntu.com/security/notices>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##

include('compat.inc');

if (description)
{
  script_id(322481);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/24");

  script_cve_id(
    "CVE-2020-29260",
    "CVE-2026-32853",
    "CVE-2026-32854",
    "CVE-2026-44988"
  );
  script_xref(name:"USN", value:"8463-1");

  script_name(english:"Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : LibVNCServer vulnerabilities (USN-8463-1)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple
vulnerabilities as referenced in the USN-8463-1 advisory.

    It was discovered that LibVNCServer had a memory leak in the client cleanup function. An attacker could
    possibly use this issue to cause LibVNCServer to consume memory, leading to a denial of service. This
    issue only affected Ubuntu 22.04 LTS. (CVE-2020-29260)

    It was discovered that LibVNCServer did not properly validate bounds when handling UltraZip encoding
    subrectangles. A remote attacker could possibly use this issue to obtain sensitive information or cause a
    denial of service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 25.04.
    (CVE-2026-32853)

    It was discovered that LibVNCServer did not properly validate return values in the HTTP proxy handlers. A
    remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of
    service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 25.04. (CVE-2026-32854)

    It was discovered that LibVNCServer did not properly handle Tight encoding gradient filter rectangles. A
    remote attacker could use this issue to cause LibVNCServer to crash, resulting in a denial of service, or
    possibly execute arbitrary code. (CVE-2026-44988)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/notices/USN-8463-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected libvncclient1, libvncserver-dev and / or libvncserver1 packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/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-2026-32853");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2022/09/02");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/06/23");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/06/24");

  script_set_attribute(attribute:"plugin_type", value:"local");
  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:canonical:ubuntu_linux:25.10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:26.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncclient1");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncserver-dev");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncserver1");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Ubuntu Local Security Checks");

  script_copyright(english:"Ubuntu Security Notice (C) 2026 Canonical, Inc. / NASL script (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('debian_package.inc');

if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Ubuntu/release');
if ( isnull(os_release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
os_release = chomp(os_release);
if (! ('22.04' >< os_release || '24.04' >< os_release || '25.10' >< os_release || '26.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 22.04 / 24.04 / 25.10 / 26.04', 'Ubuntu ' + os_release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);

var pkgs = [
    {'osver': '22.04', 'pkgname': 'libvncclient1', 'pkgver': '0.9.13+dfsg-3ubuntu0.1', 'cves': ['CVE-2020-29260', 'CVE-2026-32853', 'CVE-2026-32854', 'CVE-2026-44988']},
    {'osver': '22.04', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.13+dfsg-3ubuntu0.1', 'cves': ['CVE-2020-29260', 'CVE-2026-32853', 'CVE-2026-32854', 'CVE-2026-44988']},
    {'osver': '22.04', 'pkgname': 'libvncserver1', 'pkgver': '0.9.13+dfsg-3ubuntu0.1', 'cves': ['CVE-2020-29260', 'CVE-2026-32853', 'CVE-2026-32854', 'CVE-2026-44988']},
    {'osver': '24.04', 'pkgname': 'libvncclient1', 'pkgver': '0.9.14+dfsg-1ubuntu0.1', 'cves': ['CVE-2026-32853', 'CVE-2026-32854', 'CVE-2026-44988']},
    {'osver': '24.04', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.14+dfsg-1ubuntu0.1', 'cves': ['CVE-2026-32853', 'CVE-2026-32854', 'CVE-2026-44988']},
    {'osver': '24.04', 'pkgname': 'libvncserver1', 'pkgver': '0.9.14+dfsg-1ubuntu0.1', 'cves': ['CVE-2026-32853', 'CVE-2026-32854', 'CVE-2026-44988']},
    {'osver': '25.10', 'pkgname': 'libvncclient1', 'pkgver': '0.9.15+dfsg-1ubuntu0.1', 'cves': ['CVE-2026-44988']},
    {'osver': '25.10', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.15+dfsg-1ubuntu0.1', 'cves': ['CVE-2026-44988']},
    {'osver': '25.10', 'pkgname': 'libvncserver1', 'pkgver': '0.9.15+dfsg-1ubuntu0.1', 'cves': ['CVE-2026-44988']},
    {'osver': '26.04', 'pkgname': 'libvncclient1', 'pkgver': '0.9.15+dfsg-3ubuntu0.1', 'cves': ['CVE-2026-44988']},
    {'osver': '26.04', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.15+dfsg-3ubuntu0.1', 'cves': ['CVE-2026-44988']},
    {'osver': '26.04', 'pkgname': 'libvncserver1', 'pkgver': '0.9.15+dfsg-3ubuntu0.1', 'cves': ['CVE-2026-44988']}
];

var flag = 0;
foreach var package_array ( pkgs ) {
  var osver = NULL;
  var pkgname = NULL;
  var pkgver = NULL;
  if (!empty_or_null(package_array['osver'])) osver = package_array['osver'];
  if (!empty_or_null(package_array['pkgname'])) pkgname = package_array['pkgname'];
  if (!empty_or_null(package_array['pkgver'])) pkgver = package_array['pkgver'];
  if (!empty_or_null(package_array['cves'])) cves = package_array['cves'];
  if (osver && pkgname && pkgver) {
    if (deb_check(release:osver, prefix:pkgname, reference:pkgver, cves:cves)) flag++;
  }
}

if (flag)
{
  var extra = '';
  extra += ubuntu_report_get();
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : extra
  );
  exit(0);
}
else
{
  var tested = ubuntu_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'libvncclient1 / libvncserver-dev / libvncserver1');
}