Ubuntu 22.04 LTS / 24.04 LTS / 26.04 LTS / Pro Realtime 22.04 LTS / Pro Realtime 24.04 LTS : OpenSSH vulnerabilities (USN-8721-1)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-8721-1. 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(344614);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/10");

  script_cve_id("CVE-2026-73281", "CVE-2026-73282", "CVE-2026-73283");
  script_xref(name:"IAVA", value:"2026-A-0847");
  script_xref(name:"USN", value:"8721-1");

  script_name(english:"Ubuntu 22.04 LTS / 24.04 LTS / 26.04 LTS / Pro Realtime 22.04 LTS / Pro Realtime 24.04 LTS : OpenSSH vulnerabilities (USN-8721-1)");

  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 / 26.04 LTS / Pro Realtime 22.04 LTS / Pro Realtime 24.04 LTS host has packages
installed that are affected by multiple vulnerabilities as referenced in the USN-8721-1 advisory.

    It was discovered that OpenSSH's ssh-agent incorrectly handled interactions between agent locking and the
    [email protected] extension. A remote attacker with access to a forwarded agent connection could
    possibly use this issue to perform operations that should only be available locally, such as adding tokens
    or using keys. (CVE-2026-73281)

    It was discovered that OpenSSH's ssh client incorrectly handled concurrent remote-forwarding operations. A
    remote attacker could possibly use this issue to cause a use-after-free condition, resulting in a denial
    of service or the execution of arbitrary code. (CVE-2026-73282)

    It was discovered that OpenSSH's sshd server incorrectly applied the restrict keyword from authorized_keys
    to tunnel forwarding requests. A local attacker with an authorized key could possibly use this issue to
    bypass intended tunnel forwarding restrictions. (CVE-2026-73283)

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-8721-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/Au:N/C:P/I:P/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-73282");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/08/11");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/09/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/10");

  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:26.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:Pro:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-client");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-client-gssapi");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-server-gssapi");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-sftp-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-tests");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:ssh");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:ssh-askpass-gnome");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_set_attribute(attribute:"stig_severity", value:"I");
  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 || '26.04' >< os_release || 'Pro' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 22.04 / 24.04 / 26.04 / Pro', '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': 'openssh-client', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': '22.04', 'pkgname': 'openssh-server', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': '22.04', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': '22.04', 'pkgname': 'openssh-tests', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': '22.04', 'pkgname': 'ssh', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': '22.04', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': '24.04', 'pkgname': 'openssh-client', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': '24.04', 'pkgname': 'openssh-server', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': '24.04', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': '24.04', 'pkgname': 'openssh-tests', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': '24.04', 'pkgname': 'ssh', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': '24.04', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': '26.04', 'pkgname': 'openssh-client', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'openssh-client-gssapi', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'openssh-server', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'openssh-server-gssapi', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'openssh-tests', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'ssh', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': '26.04', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:10.2p1-2ubuntu3.6'},
    {'osver': 'Pro', 'pkgname': 'openssh-client', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': 'Pro', 'pkgname': 'openssh-server', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': 'Pro', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': 'Pro', 'pkgname': 'openssh-tests', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': 'Pro', 'pkgname': 'ssh', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': 'Pro', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:8.9p1-3ubuntu0.17'},
    {'osver': 'Pro', 'pkgname': 'openssh-client', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': 'Pro', 'pkgname': 'openssh-server', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': 'Pro', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': 'Pro', 'pkgname': 'openssh-tests', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': 'Pro', 'pkgname': 'ssh', 'pkgver': '1:9.6p1-3ubuntu13.19'},
    {'osver': 'Pro', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:9.6p1-3ubuntu13.19'}
];

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_WARNING,
    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, 'openssh-client / openssh-client-gssapi / openssh-server / etc');
}