TencentOS Server 4: freerdp (TSSA-2026:0966)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Tencent Linux Security Advisory TSSA-2026:0966.
##

include('compat.inc');

if (description)
{
  script_id(343514);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/07");

  script_cve_id("CVE-2026-55191", "CVE-2026-55193", "CVE-2026-55194");

  script_name(english:"TencentOS Server 4: freerdp (TSSA-2026:0966)");

  script_set_attribute(attribute:"synopsis", value:
"The remote TencentOS Server 4 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 4 host is prior to tested version. It is,
therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0966 advisory.

    Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:

    CVE-2026-55194:
    A flaw was found in FreeRDP. A remote attacker, specifically a malicious TS Gateway, can exploit a heap-
    buffer-overflow vulnerability by sending a specially crafted Remote Desktop Protocol (RDP) response. This
    occurs because the client incorrectly uses a smaller `alloc_hint` value instead of the actual `StubLength`
    for buffer capacity during response reassembly. This allows attacker-controlled data to be written beyond
    the intended buffer, leading to a client crash and potentially enabling arbitrary code execution.

    CVE-2026-55193:
    FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP clients using TS
    Gateway accept a server-controlled max_xmit_frag value in libfreerdp/core/gateway/rpc_bind.c without
    bounding it to the 4088-byte ReceiveFragment allocation. A malicious gateway can advertise 65535 and then
    send a response fragment of the same length, causing rpc_channel_read in libfreerdp/core/gateway/rpc.c to
    write up to 65535 bytes into the smaller ReceiveFragment buffer. This can crash the client and may permit
    code execution through attacker-controlled heap corruption. This issue is fixed in version 3.27.0.

    CVE-2026-55191:
    FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP clients that
    negotiate RDPGFX AVC444 with an H.264 decoder backend calculate the intermediate YUV444 allocation size in
    libfreerdp/codec/h264.c with 32-bit multiplication in avc444_ensure_buffer. A malicious RDP server can
    supply surface dimensions for which piDstStride multiplied by padDstHeight wraps to a small nonzero value,
    causing winpr_aligned_recalloc to allocate an undersized buffer before YUV420CombineToYUV444 writes using
    the actual stride and rectangle dimensions. This can cause a client crash and may permit code execution
    through attacker-influenced heap corruption. This issue is fixed in version 3.27.0.

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-20260966.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:C/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:R/S:U/C:H/I:H/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:P/VC:H/VI:H/VA:H/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-2026-55194");

  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:"2026/06/18");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/09/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/07");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:tencent:tencentos_server:4");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:tencent:tencentos_server:freerdp");
  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:"^4([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'TencentOS 4.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': '4',
    'pkgs': [
      {'reference':'freerdp-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-debuginfo-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-debuginfo-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-debugsource-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-debugsource-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-devel-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-devel-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-libs-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-libs-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-libs-debuginfo-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-libs-debuginfo-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-server-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-server-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-server-debuginfo-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'freerdp-server-debuginfo-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libwinpr-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libwinpr-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libwinpr-debuginfo-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libwinpr-debuginfo-2.11.6-18.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libwinpr-devel-2.11.6-18.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libwinpr-devel-2.11.6-18.tl4', '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_HOLE,
      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, 'freerdp / freerdp-debuginfo / freerdp-debugsource / etc');
}