TencentOS Server 3: openssh (TSSA-2026:0848)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Tencent Linux Security Advisory TSSA-2026:0848.
##

include('compat.inc');

if (description)
{
  script_id(335135);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/13");

  script_cve_id("CVE-2026-55653", "CVE-2026-55655");

  script_name(english:"TencentOS Server 3: openssh (TSSA-2026:0848)");

  script_set_attribute(attribute:"synopsis", value:
"The remote TencentOS Server 3 host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The version of Tencent Linux installed on the remote TencentOS Server 3 host is prior to tested version. It is,
therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0848 advisory.

    Package updates are available for TencentOS Server 3 that fix the following vulnerabilities:

    CVE-2026-55653:
    A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-
    Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing
    Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group
    parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of
    Service (DoS).

    CVE-2026-55655:
    A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side
    X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11
    forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the
    confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow
    some manipulation of the forwarded session.

Tenable has extracted the preceding description block directly from the Tencent Linux 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://mirrors.tencent.com/tlinux/errata/tssa-20260848.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/I:P/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-55655");

  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:"2026/06/23");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/07/30");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/13");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:tencent:tencentos_server:3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:tencent:tencentos_server:openssh");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Tencent 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_info2.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/etc/os-release", "Host/TencentOS/rpm-list", "Host/cpu");

  exit(0);
}


include('rpm2.inc');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_product = get_kb_item('installed_os/local/SSH/0/product');
if (isnull(os_product) || 'TencentOS' >!< os_product) audit(AUDIT_OS_NOT, 'TencentOS');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'TencentOS');
if (! preg(pattern:"^3([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'TencentOS 3.x', 'TencentOS ' + os_version);

if (!get_kb_item('Host/TencentOS/rpm-list')) 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, 'TencentOS', cpu);

var constraints = [
  {
    'release': '3',
    'pkgs': [
      {'reference':'openssh-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-askpass-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-askpass-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-askpass-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-askpass-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-cavs-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-cavs-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-cavs-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-cavs-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-clients-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-clients-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-clients-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-clients-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-debugsource-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-debugsource-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-keycat-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-keycat-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-keycat-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-keycat-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-ldap-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-ldap-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-ldap-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-ldap-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-server-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-server-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-server-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'openssh-server-debuginfo-8.0p1-30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'allowmaj':TRUE},
      {'reference':'pam_ssh_agent_auth-0.10.3-7.30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'pam_ssh_agent_auth-0.10.3-7.30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'pam_ssh_agent_auth-debuginfo-0.10.3-7.30.tl3.ap.2', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'pam_ssh_agent_auth-debuginfo-0.10.3-7.30.tl3.ap.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE}
    ]
  }
];

var os_release = get_one_kb_item('installed_os/local/SSH/0/release');
var os_sp = get_one_kb_item('Host/*/minor_release');

var flag = 0;
var reference;
var sp;
var _cpu;
var el_string;
var rpm_spec_vers_cmp;
var epoch;
var allowmaj;
var exists_check;
var cves;
foreach var constraint ( constraints ) {
  # Check that the target release is equal to the affected release
  if (!empty_or_null(constraint['release'])){
    if (constraint['release'] != os_release) continue;
  }
  if (!empty_or_null(constraint['sp'])){
    if (constraint['sp'] != os_sp) continue;
  }
  foreach var pkg ( constraint['pkgs'] ) {
    reference = NULL;
    sp = NULL;
    _cpu = NULL;
    el_string = NULL;
    rpm_spec_vers_cmp = NULL;
    epoch = NULL;
    allowmaj = NULL;
    exists_check = NULL;
    cves = NULL;
    if (!empty_or_null(pkg['reference'])) reference = pkg['reference'];
    if (!empty_or_null(pkg['sp'])) sp = pkg['sp'];
    if (!empty_or_null(pkg['cpu'])) _cpu = pkg['cpu'];
    if (!empty_or_null(pkg['el_string'])) el_string = pkg['el_string'];
    if (!empty_or_null(pkg['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = pkg['rpm_spec_vers_cmp'];
    if (!empty_or_null(pkg['epoch'])) epoch = pkg['epoch'];
    if (!empty_or_null(pkg['allowmaj'])) allowmaj = pkg['allowmaj'];
    if (!empty_or_null(pkg['exists_check'])) exists_check = pkg['exists_check'];
    if (!empty_or_null(pkg['cves'])) cves = pkg['cves'];
    if (reference &&
        ## (no known rpm to check OR known rpm_exists)
        (!exists_check || rpm_exists(rpm:exists_check)) &&
        rpm_check(sp:sp, cpu:_cpu, reference:reference, epoch:epoch, el_string:el_string, rpm_spec_vers_cmp:rpm_spec_vers_cmp, allowmaj:allowmaj, cves:cves)) flag++;
  }
}

if (flag)
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  var tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'openssh / openssh-askpass / openssh-askpass-debuginfo / etc');
}