Linux Distros Unpatched Vulnerability : CVE-2023-26485

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

include('compat.inc');

if (description)
{
  script_id(257262);
  script_version("1.8");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/21");

  script_cve_id("CVE-2023-26485");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2023-26485");

  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.

  - cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. A
    polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent
    denial of service. This CVE covers quadratic complexity issues when parsing text which leads with either
    large numbers of `_` characters. This issue has been addressed in version 0.29.0.gfm.10. Users are advised
    to upgrade. Users unable to upgrade should validate that their input comes from trusted sources. ###
    Impact A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and
    subsequent denial of service. ### Proof of concept ``` $ ~/cmark-gfm$ python3 -c 'pad = _ * 100000;
    print(pad + . + pad, end=)' | time ./build/src/cmark-gfm --to plaintext ``` Increasing the number
    10000 in the above commands causes the running time to increase quadratically. ### Patches This
    vulnerability have been patched in 0.29.0.gfm.10. ### Note on cmark and cmark-gfm XXX: TBD [cmark-
    gfm](https://github.com/github/cmark-gfm) is a fork of [cmark](https://github.com/commonmark/cmark) that
    adds the GitHub Flavored Markdown extensions. The two codebases have diverged over time, but share a
    common core. These bugs affect both `cmark` and `cmark-gfm`. ### Credit We would like to thank @gravypod
    for reporting this vulnerability. ### References https://en.wikipedia.org/wiki/Time_complexity ### For
    more information If you have any questions or comments about this advisory: * Open an issue in
    [github/cmark-gfm](https://github.com/github/cmark-gfm) (CVE-2023-26485)

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-2023-26485");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2023-26485");
  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:M/Au:N/C:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:POC/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:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2023-26485");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2023/03/31");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/08/27");

  script_set_attribute(attribute:"plugin_type", value:"local");
  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:25.04");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:25.10");
  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:"p-cpe:/a:canonical:ubuntu_linux:cmark");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:cmark-gfm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:python-cmarkgfm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:r-cran-commonmark");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:ruby-commonmarker");
  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) 2025-2026 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/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-25.04", "Host/OS/Ubuntu Linux-25.10");

  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": "cmark-gfm"},
          {"reference": "libcmark-gfm-dev"},
          {"reference": "libcmark-gfm-extensions-dev"},
          {"reference": "libcmark-gfm-extensions0.29.0.gfm.6"},
          {"reference": "libcmark-gfm0.29.0.gfm.6"},
          {"reference": "python3-cmarkgfm"},
          {"reference": "r-cran-commonmark"},
          {"reference": "ruby-commonmarker"}
        ]
      }
    ]
  },
  "Debian Linux-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "pkgs": [
          {"reference": "cmark-gfm"},
          {"reference": "libcmark-gfm-dev"},
          {"reference": "libcmark-gfm-extensions-dev"},
          {"reference": "libcmark-gfm-extensions0"},
          {"reference": "libcmark-gfm0"},
          {"reference": "python3-cmarkgfm"},
          {"reference": "r-cran-commonmark"},
          {"reference": "ruby-commonmarker"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "cmark"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "cmark"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "cmark"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "cmark"}
        ]
      }
    ]
  },
  "Ubuntu Linux-25.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "25.04",
        "pkgs": [
          {"reference": "cmark"}
        ]
      }
    ]
  },
  "Ubuntu Linux-25.10": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "25.10",
        "pkgs": [
          {"reference": "cmark"}
        ]
      }
    ]
  }
};

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 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');
}