Debian dla-4535 : openssh-client - security update

#%NASL_MIN_LEVEL 80900
#
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Debian Security Advisory dla-4535. The text
# itself is copyright (C) Software in the Public Interest, Inc.
#

include('compat.inc');

if (description)
{
  script_id(307622);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/04/20");

  script_cve_id("CVE-2026-3497");

  script_name(english:"Debian dla-4535 : openssh-client - security update");

  script_set_attribute(attribute:"synopsis", value:
"The remote Debian host is missing a security-related update.");
  script_set_attribute(attribute:"description", value:
"The remote Debian 11 host has packages installed that are affected by a vulnerability as referenced in the dla-4535
advisory.

    - -------------------------------------------------------------------------
    Debian LTS Advisory DLA-4535-1                [email protected]
    https://www.debian.org/lts/security/               Emilio Pozuelo Monfort
    April 16, 2026                                https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : openssh
    Version        : 1:8.4p1-5+deb11u6
    CVE ID         : CVE-2026-3497
    Debian Bug     : 1130595

    Jeremy Brown discovered a flaw in the GSSAPI Key Exchange patch applied
    in Debian to OpenSSH, an implementation of the SSH protocol suite,
    affecting non-default configurations with the GSSAPIKeyExchange setting
    enabled. A remote attacker can take advantage of this flaw to cause a
    denial of service, or potentially the execution of arbitrary code.

    For Debian 11 bullseye, this problem has been fixed in version
    1:8.4p1-5+deb11u6.

    We recommend that you upgrade your openssh packages.

    For the detailed security status of openssh please refer to
    its security tracker page at:
    https://security-tracker.debian.org/tracker/openssh

    Further information about Debian LTS security advisories, how to apply
    these updates to your system and frequently asked questions can be
    found at: https://wiki.debian.org/LTS

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

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/source-package/openssh");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-3497");
  script_set_attribute(attribute:"see_also", value:"https://packages.debian.org/source/bullseye/openssh");
  script_set_attribute(attribute:"solution", value:
"Upgrade the openssh-client packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/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:N/VI:L/VA:L/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-3497");

  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:"2026/03/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/04/16");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/04/20");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh-client");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh-client-udeb");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh-server-udeb");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh-sftp-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh-tests");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:ssh");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:ssh-askpass-gnome");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Debian/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);
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);

var debian_release = get_kb_item('Host/Debian/release');
if ( isnull(debian_release) ) audit(AUDIT_OS_NOT, 'Debian');
debian_release = chomp(debian_release);
if (! preg(pattern:"^(11)\.[0-9]+", string:debian_release)) audit(AUDIT_OS_NOT, 'Debian 11.0', 'Debian ' + debian_release);
var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Debian', cpu);

var pkgs = [
    {'release': '11.0', 'prefix': 'openssh-client', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'openssh-client-udeb', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'openssh-server', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'openssh-server-udeb', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'openssh-sftp-server', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'openssh-tests', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'ssh', 'reference': '1:8.4p1-5+deb11u6'},
    {'release': '11.0', 'prefix': 'ssh-askpass-gnome', 'reference': '1:8.4p1-5+deb11u6'}
];

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

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : deb_report_get()
  );
  exit(0);
}
else
{
  var tested = deb_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'openssh-client / openssh-client-udeb / openssh-server / etc');
}