TencentOS Server 2: libssh2 (TSSA-2026:1355)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Tencent Linux Security Advisory TSSA-2026:1355.
##

include('compat.inc');

if (description)
{
  script_id(375729);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/11/04");

  script_cve_id(
    "CVE-2026-7598",
    "CVE-2026-58050",
    "CVE-2026-66032",
    "CVE-2026-66034"
  );
  script_xref(name:"IAVA", value:"2026-A-0788");

  script_name(english:"TencentOS Server 2: libssh2 (TSSA-2026:1355)");

  script_set_attribute(attribute:"synopsis", value:
"The remote TencentOS Server 2 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 2 host is prior to tested version. It is,
therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:1355 advisory.

    Package updates are available for TencentOS Server 2 that fix the following vulnerabilities:

    CVE-2026-7598:
    A security vulnerability has been detected in libssh2 up to 1.11.1. The impacted element is the function
    userauth_password of the file src/userauth.c. Such manipulation of the argument username_len/password_len
    leads to integer overflow. The attack may be launched remotely. The name of the patch is
    256d04b60d80bf1190e96b0ad1e91b2174d744b1. A patch should be applied to remediate this issue.

    CVE-2026-58050:
    libssh2 through 1.11.1 reads an attacker-controlled 32-bit attribute count from a publickey-subsystem
    response and uses it in the allocation num_attrs * sizeof(libssh2_publickey_attribute) without bounds
    checking, so on 32-bit platforms the multiplication overflows to an undersized buffer. A malicious SSH
    server can then drive the attribute-parsing loop to write past the allocation, causing a heap buffer
    overflow in a connecting libssh2 client.

    CVE-2026-66032:
    libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open()
    function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client
    opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the
    response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error
    such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache
    dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.

    CVE-2026-66034:
    libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows
    a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an
    uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1
    response parser reads a server-controlled comment_len value and advances the parse pointer without
    verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from
    adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup
    path frees an uninitialized pointer from a non-zeroed realloc() region.

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-20261355.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  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:N/S:U/C:N/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: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:P");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-7598");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2026-58050");
  script_set_attribute(attribute:"cvss4_score_source", value:"CVE-2026-66032");

  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:"2026/05/01");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/31");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/11/04");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:tencent:tencentos_server:2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:tencent:tencentos_server:libssh2");
  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:"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:"^2([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'TencentOS 2.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': '2',
    'pkgs': [
      {'reference':'libssh2-1.8.0-4.tl2.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libssh2-debuginfo-1.8.0-4.tl2.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libssh2-devel-1.8.0-4.tl2.2', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libssh2-docs-1.8.0-4.tl2.2', '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, 'libssh2 / libssh2-debuginfo / libssh2-devel / etc');
}