Xen Hypervisor TLB Flush Request Handling Race Condition System Memory Access Guest-to-Host Privilege Escalation (XSA-241)

#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(103976);
  script_version("1.7");
  script_set_attribute(attribute:"plugin_modification_date", value:"2021/06/03");

  script_cve_id(
    "CVE-2017-15588",
    "CVE-2017-15589",
    "CVE-2017-15590",
    "CVE-2017-15591",
    "CVE-2017-15592",
    "CVE-2017-15593",
    "CVE-2017-15594",
    "CVE-2017-15595",
    "CVE-2017-15596"
  );
  script_bugtraq_id(101490, 101496, 101500);
  script_xref(name:"IAVB", value:"2017-B-0142-S");

  script_name(english:"Xen Hypervisor TLB Flush Request Handling Race Condition System Memory Access Guest-to-Host Privilege Escalation (XSA-241)");
  script_summary(english:"Checks 'xl info' output for the Xen hypervisor version.");

  script_set_attribute(attribute:"synopsis", value:
"The remote Xen hypervisor installation is missing a security update.");
  script_set_attribute(attribute:"description", value:
"According to its self-reported version number, the Xen hypervisor
installed on the remote host is affected by a race condition that is
triggered when handling TLB flush requests. This allows an attacker on
the guest to access all system memory,  allowing them to cause a
denial of service, disclose sensitive information, or gain elevated
privileges on the host.

Note that Nessus has checked the changeset versions based on the
xen.git change log. Nessus did not check guest hardware configurations
or if patches were applied manually to the source code before a
recompile and reinstall.");
  script_set_attribute(attribute:"see_also", value:"http://xenbits.xen.org/xsa/advisory-241.html");
  script_set_attribute(attribute:"see_also", value:"https://xenbits.xen.org/gitweb/?p=xen.git;a=summary");
  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:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2017-15595");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/10/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/10/12");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/10/19");

  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) 2017-2021 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("audit.inc");
include("global_settings.inc");
include("install_func.inc");
include("misc_func.inc");

app_name = "Xen Hypervisor";
install  = get_single_install(app_name:app_name);
if (report_paranoia < 2) audit(AUDIT_PARANOID);

version         = install['version'];
display_version = install['display_version'];
path            = install['path'];
managed_status  = install['Managed status'];
changeset       = install['Changeset'];

if (!empty_or_null(changeset))
  display_version += " (changeset " + changeset + ")";

# Installations that are vendor-managed are handled by OS-specific local package checks
if (managed_status == "managed")
  audit(AUDIT_INST_PATH_NOT_VULN, app_name, display_version, path);

# XSA-241
fixes['4.5']['fixed_ver']           = '4.5.5';
fixes['4.5']['fixed_ver_display']   = '4.5.5 (changeset da4f24d)';
fixes['4.5']['affected_ver_regex']  = '^4\\.5\\.';
fixes['4.5']['affected_changesets'] = make_list("b7582ac", "196371c",
  "7afc8ad", "72c107b", "5659aa5", "a224de6", "6442fa9", "db487a6",
  "709230f", "83724d9", "04b8c4c", "0b2ceae", "e3f0768", "d5a5231",
  "c5b0fe5", "136ff4e", "42c8ba5", "d38489d", "df59014", "3217129",
  "4964e86", "c079597", "6ec173b", "a373456", "0780e81", "e5ef76d",
  "25eaa86", "ae02360", "5597df9", "c5de05e", "773094e", "e39a248",
  "7b3712a", "be35327", "8825df1", "d7e3725", "6eb61e4", "b1fcfed",
  "5779d6a", "afdd77e", "c18367a", "7b7fd80", "b30e165", "62ef9b2",
  "8071724", "235b5d5", "a28b99d", "ff294fc", "bc01e2d", "da50922",
  "386cc94", "139960f", "ec3ddd6", "988929a", "1c48dff", "20d4248",
  "9610422", "cd76cd3", "455fd66", "b820c31", "ac3d8bc", "cde86fc",
  "1678521", "83cb2db", "43d06ef", "2b17bf4", "1a2bda5", "0bd7faf",
  "e3426e2", "37281bc", "27be856", "bdf3ef1", "cc325c0", "8e7b84d",
  "387b8ae", "34fbae7", "1530da2", "274a1f6", "b679cfa", "877b760",
  "cfe165d", "84e4e56", "e4ae4b0");

fixes['4.6']['fixed_ver']           = '4.6.6';
fixes['4.6']['fixed_ver_display']   = '4.6.6 (changeset 57318e1)';
fixes['4.6']['affected_ver_regex']  = '^4\\.6\\.';
fixes['4.6']['affected_changesets'] = make_list("9f22d72", "e0353b4",
  "76f1549", "9bac910", "c7a43e3", "913d4f8", "c5881c5", "b0239cd",
  "78fd0c3", "9079e0d", "1658a87", "22b6dfa", "a8cd231", "629eddd",
  "64c03bb", "b4660b4", "1ac8162", "747df3c", "5ae011e", "f974d32",
  "3300ad3", "d708b69");

fixes['4.7']['fixed_ver']           = '4.7.4';
fixes['4.7']['fixed_ver_display']   = '4.7.4-pre (changeset 5ca7d11)';
fixes['4.7']['affected_ver_regex']  = '^4\\.7\\.';
fixes['4.7']['affected_changesets'] = make_list("ebd47d4", "6a6a339",
  "e61be54", "e3f7a64", "957ad23", "b1ae705", "3add76f", "314a8fc",
  "d6aad63", "7c99633", "145c18d", "c3fa5cd", "487f8f9", "ffcfc40",
  "c7783d9", "3331050", "83966a3", "a67b223", "68dbba2", "2728470",
  "dea68ed", "9d12253", "73d7bc5", "b704b1a", "ca4ef7b", "ece330a",
  "3d63ebc", "30d50f8", "2dc3cdb", "5151257", "c9f3ca0", "e873251",
  "8aebf85", "c362cde", "fece08a");

fixes['4.8']['fixed_ver']           = '4.8.3';
fixes['4.8']['fixed_ver_display']   = '4.8.3-pre (changeset df89197)';
fixes['4.8']['affected_ver_regex']  = '^4\\.8\\.';
fixes['4.8']['affected_changesets'] = make_list("c4f969d", "b1f3f1d",
  "7251c06", "1960ca8", "866cfa1", "ddd6e41", "370cc9a", "39e3024",
  "9f092f5", "667f70e", "2116fec", "1a535c3", "ee3fc24", "d623d82",
  "dda458c", "c642b12", "80d7ef3", "ff4f60a", "36898eb", "4d7ccae",
  "e574046", "90dafa4", "c020cf2");

fixes['4.9']['fixed_ver']           = '4.9.1';
fixes['4.9']['fixed_ver_display']   = '4.9.1-pre (changeset 61a2d31)';
fixes['4.9']['affected_ver_regex']  = '^4\\.9\\.';
fixes['4.9']['affected_changesets'] = make_list("c2b0a92", "d842630",
  "ef61bcf", "44ceb19", "ae45442", "784afd9", "22032b2", "58da67f",
  "d1b64cc", "9cde7a8", "1cdcb36", "84c039e", "b244ac9", "612044a",
  "e8fd372", "a568e25", "8fef83e", "478e40c", "22ea731", "e7703a2",
  "91ded3b", "2cc3d32", "79775f5", "43cb0c4", "4821228", "d23bcc5",
  "308654c", "6fd84b3", "89b36cc", "a9ecd60", "798f6c9", "6508278",
  "5587d9a", "527fc5c", "5ff1de3", "692ed82", "9bf14bb", "c57b1f9",
  "6b147fd", "0e186e3", "afc5ebf", "266fc0e", "4698106", "f4f02f1",
  "0fada05", "ab4eb6c", "b29ecc7", "a11d14b", "107401e", "1b7834a");

fix = NULL;
foreach ver_branch (keys(fixes))
{
  if (version =~ fixes[ver_branch]['affected_ver_regex'])
  {
    ret = ver_compare(ver:version, fix:fixes[ver_branch]['fixed_ver']);
    if (ret < 0)
      fix = fixes[ver_branch]['fixed_ver_display'];
    else if (ret == 0)
    {
      if (empty_or_null(changeset))
        fix = fixes[ver_branch]['fixed_ver_display'];
      else
        foreach affected_changeset (fixes[ver_branch]['affected_changesets'])
          if (changeset == affected_changeset)
            fix = fixes[ver_branch]['fixed_ver_display'];
    }
  }
}

if (empty_or_null(fix))
  audit(AUDIT_INST_PATH_NOT_VULN, app_name, display_version, path);

items  = make_array("Installed version", display_version,
                    "Fixed version", fix,
                    "Path", path);
order  = make_list("Path", "Installed version", "Fixed version");
report = report_items_str(report_items:items, ordered_fields:order) + '\n';

security_report_v4(port:0, extra:report, severity:SECURITY_HOLE);