Xen: Xenstored DoS by unprivileged domain (XSA-481)

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

include('compat.inc');

if (description)
{
  script_id(318808);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/08");

  script_cve_id("CVE-2026-23555");
  script_xref(name:"IAVB", value:"2026-B-0069");

  script_name(english:"Xen: Xenstored DoS by unprivileged domain (XSA-481)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Xen hypervisor installation is missing a security update.");
  script_set_attribute(attribute:"description", value:
"Any guest issuing a Xenstore command accessing a node using the (illegal) node path '/local/domain/', will crash
xenstored due to a clobbered error indicator in xenstored when verifying the node path. Note that the crash is
forced via a failing assert() statement in xenstored. In case xenstored is being built with NDEBUG #defined, an
unprivileged guest trying to access the node path '/local/domain/' will result in it no longer being serviced by
xenstored, other guests (including dom0) will still be serviced, but xenstored will use up all cpu time it can get.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://xenbits.xenproject.org/xsa/advisory-481.html");
  script_set_attribute(attribute:"solution", value:
"Apply the appropriate patch according to the vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:N/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-23555");

  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:"2026/03/17");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/03/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/06/05");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:xen:xen");
  script_set_attribute(attribute:"stig_severity", value:"I");
  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("xen_server_detect.nbin");
  script_require_keys("installed_sw/Xen Hypervisor", "Settings/ParanoidReport");

  exit(0);
}

include('vcf.inc');
include('vcf_extras.inc');

var fixes;
var app = 'Xen Hypervisor';
var app_info = vcf::xen_hypervisor::get_app_info(app:app);
if (report_paranoia < 2) audit(AUDIT_PARANOID);

fixes['4.18']['fixed_ver']           = '4.18.5';
fixes['4.18']['fixed_ver_display']   = '4.18.5 (changeset 2c5f7fd)';
fixes['4.18']['affected_ver_regex']  = "^4\.18([^0-9]|$)";
fixes['4.18']['affected_changesets'] = make_list('8b8c324', 'ec8251e',
  'd477525', 'f196c2f', '502d206', '343379c', 'd15515f', 'f6b0a04',
  '4112b5c', '8746612', 'f0fcf69', 'd04a36f', 'a52a373', '832ecbf',
  '9143406', '1ac5088', 'c90cec6', '46c0b23', '2102093', 'de89b16',
  'aba830f', '5119086', '25a125c', '13d3020', 'd8cab42', '41b62f8',
  '82c302a', 'b6266b2', 'cd46db2', '9c0becc', '9548f45', '2ec55f6',
  'df49dab', '709a223', '8b348e9', '60820cd', 'dcc9c3a', '43c513c',
  '8fc76b1', 'e9d112e', '460ece3', '438bb12', '0b8f769');

fixes['4.19']['fixed_ver']           = '4.19.5';
fixes['4.19']['fixed_ver_display']   = '4.19.5-pre (changeset 7e16c85)';
fixes['4.19']['affected_ver_regex']  = "^4\.19([^0-9]|$)";
fixes['4.19']['affected_changesets'] = make_list('b4993d7', '638f4f8',
  'da800c1', '8f71585', '49068c5', 'a38f515', '260740e', 'b74f88c',
  '84b0068', '24c8308', 'aa07351', '744d8cf', '2d88bf5', '6804451',
  'bd3a5c4', '8656965', '60f5b47', '2fd8436', '52f3b7c', '49a4deb',
  '2f7bd87', '7f9cde0', '991f480', '6b4480f', 'fad76f0', '9192605',
  '7482ce0', '489b5bb', '4eb4bb4', '495cfdc', 'a9d58e5', 'fb0dd88',
  'bc8363a', '999fdfb', '072dbe7', '9135f73', 'c2affd2', '40c5e35',
  '331ffed');

vcf::xen_hypervisor::check_version_and_report(app_info:app_info, fixes:fixes, severity:SECURITY_WARNING);