Linux Distros Unpatched Vulnerability : CVE-2026-19487

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

include('compat.inc');

if (description)
{
  script_id(335368);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/14");

  script_cve_id("CVE-2026-19487");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-19487");

  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.

  - Perl versions from 5.9.4 before 5.41.9 produce incorrect regular expression match results when a stale
    failure flag ends the Aho-Corasick prescan early in S_find_byclass. The prescan walks the subject for
    positions where the full pattern could match, and the engine tries it from the leftmost one recorded. A
    failing transition sets the failed flag, and a later successful transition does not clear it, so the
    prescan reads the stale flag as a failure and stops before it can record a candidate that starts earlier.
    It takes a subject where one candidate is recorded and a later character then forces a fallback through a
    fail link that succeeds. Example: ABCDE =~ m/ABCF|BCDE|C/; # matches C at offset 2, not BCDE ABCDE =~
    m/ABCF|BCDE|C(G)/; # no match, BCDE missed An alternation like this can miss input it should match, or
    match it on the wrong branch, so an access or filtering decision made from the result can be wrong.
    (CVE-2026-19487)

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-2026-19487");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-19487");
  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:N/AC:L/Au:N/C:N/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/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:L");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-19487");

  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:"2026/08/13");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/14");

  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:11.0");
  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:perl");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:perl");
  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-11", "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": "libperl-dev"},
          {"reference": "libperl5.36"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.36"}
        ]
      }
    ]
  },
  "Debian Linux-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.32"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.32"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.40"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.40"}
        ]
      }
    ]
  },
  "Ubuntu Linux-26.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "26.04",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.40"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.40"}
        ]
      }
    ]
  },
  "Ubuntu Linux-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "libcgi-fast-perl"},
          {"reference": "libperl-dev"},
          {"reference": "libperl5.18"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.22"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.22"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.26"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.26"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.30"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.30"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.34"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.34"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "libperl-dev"},
          {"reference": "libperl5.38t64"},
          {"reference": "perl"},
          {"reference": "perl-base"},
          {"reference": "perl-debug"},
          {"reference": "perl-doc"},
          {"reference": "perl-modules-5.38"}
        ]
      }
    ]
  }
};

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');
}