Xen: Use after free of paging structures in EPT (XSA-480)

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

include('compat.inc');

if (description)
{
  script_id(318807);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/08");

  script_cve_id("CVE-2026-23554");
  script_xref(name:"IAVB", value:"2026-B-0069");

  script_name(english:"Xen: Use after free of paging structures in EPT (XSA-480)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Xen hypervisor installation is missing a security update.");
  script_set_attribute(attribute:"description", value:
"The Intel EPT paging code uses an optimization to defer flushing of any cached EPT state until the p2m lock is
dropped, so that multiple modifications done under the same locked region only issue a single flush. Freeing of
paging structures however is not deferred until the flushing is done, and can result in freed pages transiently
being present in cached state. Such stale entries can point to memory ranges not owned by the guest, thus allowing
access to unintended memory regions.

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-480.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:H/Au:S/C:C/I:C/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:H/PR:L/UI:N/S:C/C:H/I:H/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-2026-23554");

  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['4.17']['fixed_ver']           = '4.17.6';
fixes['4.17']['fixed_ver_display']   = '4.17.6 (changeset ca4c5d8)';
fixes['4.17']['affected_ver_regex']  = "^4\.17([^0-9]|$)";
fixes['4.17']['affected_changesets'] = make_list('36e6dcb', 'a2bca55',
  '87567b0', '8f29c76', '8c80ec8');

fixes['4.18']['fixed_ver']           = '4.18.5';
fixes['4.18']['fixed_ver_display']   = '4.18.5 (changeset 8b8c324)';
fixes['4.18']['affected_ver_regex']  = "^4\.18([^0-9]|$)";
fixes['4.18']['affected_changesets'] = make_list('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 b4993d7)';
fixes['4.19']['affected_ver_regex']  = "^4\.19([^0-9]|$)";
fixes['4.19']['affected_changesets'] = make_list('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);