Linux Distros Unpatched Vulnerability : CVE-2026-84308

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(342554);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/04");

  script_cve_id("CVE-2026-84308");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-84308");

  script_set_attribute(attribute:"synopsis", value:
"The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be
patched.");
  script_set_attribute(attribute:"description", value:
"The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied
patch available.

  - phpseclib is a PHP secure communications library. Prior to 3.0.57 and 4.0.1, pure-PHP X25519 scalar
    multiplication in phpseclib/Math/PrimeField/Integer.php performs data-dependent conditional modular
    reductions in add() and subtract(). During the Montgomery ladder in
    phpseclib/Crypt/EC/BaseCurves/Montgomery.php, the reduction behavior of each step depends on the secret
    scalar prefix, creating per-step timing and libgmp call-count observations that can reveal a reused
    251-bit clamped private scalar. The phpseclib/Crypt/EC/Formats/Keys/MontgomeryPrivate.php derivation path
    invokes the pure-PHP multiplication without a native-engine check, while
    phpseclib/Crypt/EC/Formats/Keys/PKCS8.php reaches it when ext-sodium is unavailable. Exploitation requires
    a reused or long-lived X25519 private key, knowledge of the corresponding public key, execution of the
    pure-PHP path, and a local observer capable of resolving individual ladder steps or libgmp entry-point
    calls. Ephemeral X25519 keys, including phpseclib's normal SSH exchange path, are not affected. Recovery
    of the scalar permanently compromises operations that reuse that key. This issue is fixed in versions
    3.0.57 and 4.0.1. (CVE-2026-84308)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-84308");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-84308");
  script_set_attribute(attribute:"solution", value:
"There is no known solution at this time.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:H/Au:S/C:C/I:C/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-84308");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/09/01");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/03");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:14.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  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:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:13.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:php5");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:php7.2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:php7.4");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:php8.1");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:php8.3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:php8.5");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:phpseclib");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:php-phpseclib3");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  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", "set_linux_os_id.nasl");
  script_require_keys("Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched", "Host/OS/identifier");
  script_require_ports("Host/OS/Debian Linux-12", "Host/OS/Debian Linux-13", "Host/OS/Ubuntu Linux-14.04", "Host/OS/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04", "Host/OS/Ubuntu Linux-24.04", "Host/OS/Ubuntu Linux-26.04");

  exit(0);
}

if (!get_kb_item("global_settings/vendor_unpatched")) exit(0, "Unpatched Vulnerabilities Detection not active.");
if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (empty_or_null(get_one_kb_item("Host/Debian/dpkg-l"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "php-phpseclib3"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "php-phpseclib3"}
        ]
      }
    ]
  },
  "Ubuntu Linux-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "libapache2-mod-php5"},
          {"reference": "libapache2-mod-php5filter"},
          {"reference": "libphp5-embed"},
          {"reference": "php-pear"},
          {"reference": "php5"},
          {"reference": "php5-cgi"},
          {"reference": "php5-cli"},
          {"reference": "php5-common"},
          {"reference": "php5-curl"},
          {"reference": "php5-dbg"},
          {"reference": "php5-dev"},
          {"reference": "php5-enchant"},
          {"reference": "php5-fpm"},
          {"reference": "php5-gd"},
          {"reference": "php5-gmp"},
          {"reference": "php5-intl"},
          {"reference": "php5-ldap"},
          {"reference": "php5-mysql"},
          {"reference": "php5-mysqlnd"},
          {"reference": "php5-odbc"},
          {"reference": "php5-pgsql"},
          {"reference": "php5-pspell"},
          {"reference": "php5-readline"},
          {"reference": "php5-recode"},
          {"reference": "php5-snmp"},
          {"reference": "php5-sqlite"},
          {"reference": "php5-sybase"},
          {"reference": "php5-tidy"},
          {"reference": "php5-xmlrpc"},
          {"reference": "php5-xsl"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "phpseclib"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "libapache2-mod-php7.2"},
          {"reference": "libphp7.2-embed"},
          {"reference": "php7.2"},
          {"reference": "php7.2-bcmath"},
          {"reference": "php7.2-bz2"},
          {"reference": "php7.2-cgi"},
          {"reference": "php7.2-cli"},
          {"reference": "php7.2-common"},
          {"reference": "php7.2-curl"},
          {"reference": "php7.2-dba"},
          {"reference": "php7.2-dev"},
          {"reference": "php7.2-enchant"},
          {"reference": "php7.2-fpm"},
          {"reference": "php7.2-gd"},
          {"reference": "php7.2-gmp"},
          {"reference": "php7.2-imap"},
          {"reference": "php7.2-interbase"},
          {"reference": "php7.2-intl"},
          {"reference": "php7.2-json"},
          {"reference": "php7.2-ldap"},
          {"reference": "php7.2-mbstring"},
          {"reference": "php7.2-mysql"},
          {"reference": "php7.2-odbc"},
          {"reference": "php7.2-opcache"},
          {"reference": "php7.2-pgsql"},
          {"reference": "php7.2-phpdbg"},
          {"reference": "php7.2-pspell"},
          {"reference": "php7.2-readline"},
          {"reference": "php7.2-recode"},
          {"reference": "php7.2-snmp"},
          {"reference": "php7.2-soap"},
          {"reference": "php7.2-sqlite3"},
          {"reference": "php7.2-sybase"},
          {"reference": "php7.2-tidy"},
          {"reference": "php7.2-xml"},
          {"reference": "php7.2-xmlrpc"},
          {"reference": "php7.2-xsl"},
          {"reference": "php7.2-zip"},
          {"reference": "phpseclib"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "libapache2-mod-php7.4"},
          {"reference": "libphp7.4-embed"},
          {"reference": "php7.4"},
          {"reference": "php7.4-bcmath"},
          {"reference": "php7.4-bz2"},
          {"reference": "php7.4-cgi"},
          {"reference": "php7.4-cli"},
          {"reference": "php7.4-common"},
          {"reference": "php7.4-curl"},
          {"reference": "php7.4-dba"},
          {"reference": "php7.4-dev"},
          {"reference": "php7.4-enchant"},
          {"reference": "php7.4-fpm"},
          {"reference": "php7.4-gd"},
          {"reference": "php7.4-gmp"},
          {"reference": "php7.4-imap"},
          {"reference": "php7.4-interbase"},
          {"reference": "php7.4-intl"},
          {"reference": "php7.4-json"},
          {"reference": "php7.4-ldap"},
          {"reference": "php7.4-mbstring"},
          {"reference": "php7.4-mysql"},
          {"reference": "php7.4-odbc"},
          {"reference": "php7.4-opcache"},
          {"reference": "php7.4-pgsql"},
          {"reference": "php7.4-phpdbg"},
          {"reference": "php7.4-pspell"},
          {"reference": "php7.4-readline"},
          {"reference": "php7.4-snmp"},
          {"reference": "php7.4-soap"},
          {"reference": "php7.4-sqlite3"},
          {"reference": "php7.4-sybase"},
          {"reference": "php7.4-tidy"},
          {"reference": "php7.4-xml"},
          {"reference": "php7.4-xmlrpc"},
          {"reference": "php7.4-xsl"},
          {"reference": "php7.4-zip"},
          {"reference": "phpseclib"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "libapache2-mod-php7.4"},
          {"reference": "libapache2-mod-php8.0"},
          {"reference": "libapache2-mod-php8.1"},
          {"reference": "libphp8.1-embed"},
          {"reference": "php8.1"},
          {"reference": "php8.1-bcmath"},
          {"reference": "php8.1-bz2"},
          {"reference": "php8.1-cgi"},
          {"reference": "php8.1-cli"},
          {"reference": "php8.1-common"},
          {"reference": "php8.1-curl"},
          {"reference": "php8.1-dba"},
          {"reference": "php8.1-dev"},
          {"reference": "php8.1-enchant"},
          {"reference": "php8.1-fpm"},
          {"reference": "php8.1-gd"},
          {"reference": "php8.1-gmp"},
          {"reference": "php8.1-imap"},
          {"reference": "php8.1-interbase"},
          {"reference": "php8.1-intl"},
          {"reference": "php8.1-ldap"},
          {"reference": "php8.1-mbstring"},
          {"reference": "php8.1-mysql"},
          {"reference": "php8.1-odbc"},
          {"reference": "php8.1-opcache"},
          {"reference": "php8.1-pgsql"},
          {"reference": "php8.1-phpdbg"},
          {"reference": "php8.1-pspell"},
          {"reference": "php8.1-readline"},
          {"reference": "php8.1-snmp"},
          {"reference": "php8.1-soap"},
          {"reference": "php8.1-sqlite3"},
          {"reference": "php8.1-sybase"},
          {"reference": "php8.1-tidy"},
          {"reference": "php8.1-xml"},
          {"reference": "php8.1-xsl"},
          {"reference": "php8.1-zip"},
          {"reference": "phpseclib"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "libapache2-mod-php8.3"},
          {"reference": "libphp8.3-embed"},
          {"reference": "php8.3"},
          {"reference": "php8.3-bcmath"},
          {"reference": "php8.3-bz2"},
          {"reference": "php8.3-cgi"},
          {"reference": "php8.3-cli"},
          {"reference": "php8.3-common"},
          {"reference": "php8.3-curl"},
          {"reference": "php8.3-dba"},
          {"reference": "php8.3-dev"},
          {"reference": "php8.3-enchant"},
          {"reference": "php8.3-fpm"},
          {"reference": "php8.3-gd"},
          {"reference": "php8.3-gmp"},
          {"reference": "php8.3-imap"},
          {"reference": "php8.3-interbase"},
          {"reference": "php8.3-intl"},
          {"reference": "php8.3-ldap"},
          {"reference": "php8.3-mbstring"},
          {"reference": "php8.3-mysql"},
          {"reference": "php8.3-odbc"},
          {"reference": "php8.3-opcache"},
          {"reference": "php8.3-pgsql"},
          {"reference": "php8.3-phpdbg"},
          {"reference": "php8.3-pspell"},
          {"reference": "php8.3-readline"},
          {"reference": "php8.3-snmp"},
          {"reference": "php8.3-soap"},
          {"reference": "php8.3-sqlite3"},
          {"reference": "php8.3-sybase"},
          {"reference": "php8.3-tidy"},
          {"reference": "php8.3-xml"},
          {"reference": "php8.3-xsl"},
          {"reference": "php8.3-zip"},
          {"reference": "phpseclib"}
        ]
      }
    ]
  },
  "Ubuntu Linux-26.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "26.04",
        "pkgs": [
          {"reference": "libapache2-mod-php8.5"},
          {"reference": "libphp8.5-embed"},
          {"reference": "php8.5"},
          {"reference": "php8.5-bcmath"},
          {"reference": "php8.5-bz2"},
          {"reference": "php8.5-cgi"},
          {"reference": "php8.5-cli"},
          {"reference": "php8.5-common"},
          {"reference": "php8.5-curl"},
          {"reference": "php8.5-dba"},
          {"reference": "php8.5-dev"},
          {"reference": "php8.5-enchant"},
          {"reference": "php8.5-fpm"},
          {"reference": "php8.5-gd"},
          {"reference": "php8.5-gmp"},
          {"reference": "php8.5-interbase"},
          {"reference": "php8.5-intl"},
          {"reference": "php8.5-ldap"},
          {"reference": "php8.5-litespeed"},
          {"reference": "php8.5-mbstring"},
          {"reference": "php8.5-mysql"},
          {"reference": "php8.5-odbc"},
          {"reference": "php8.5-pgsql"},
          {"reference": "php8.5-phpdbg"},
          {"reference": "php8.5-readline"},
          {"reference": "php8.5-snmp"},
          {"reference": "php8.5-soap"},
          {"reference": "php8.5-sqlite3"},
          {"reference": "php8.5-sybase"},
          {"reference": "php8.5-tidy"},
          {"reference": "php8.5-xml"},
          {"reference": "php8.5-xsl"},
          {"reference": "php8.5-zip"},
          {"reference": "phpseclib"}
        ]
      }
    ]
  }
};

var distro_constraints_values = linux_unpatched::get_distro_constraints(distro_constraints_arr:distro_constraints_array);
if (empty_or_null(distro_constraints_values)) audit(AUDIT_HOST_NOT, 'affected');

var third_party_support = get_kb_item('Host/OS/extended-third-party');
if (!empty_or_null(third_party_support)) {
    var third_party_vendors = distro_constraints_values['third_party'];
    if (!empty_or_null(third_party_vendors)) {
        var vendor;
        foreach vendor (third_party_vendors) {
            if (vendor == third_party_support) exit(0, 'A third party management patch is available for this vulnerability from ' + vendor + '.\n');
        }
    }
}

var report = linux_unpatched::check_unpatched_constraints(distro_constraints_values:distro_constraints_values);

if (!empty_or_null(report))
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}