Arista Networks EOS 802.1X Per-Supplicant ACL Bypass (SA0150) (CVE-2026-77191)

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

include('compat.inc');

if (description)
{
  script_id(346255);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/18");

  script_cve_id("CVE-2026-77191");
  script_xref(name:"IAVA", value:"2026-A-0986");

  script_name(english:"Arista Networks EOS 802.1X Per-Supplicant ACL Bypass (SA0150) (CVE-2026-77191)");

  script_set_attribute(attribute:"synopsis", value:
"The version of Arista Networks EOS running on the remote device is affected by an access control bypass
vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Arista Networks EOS running on the remote device is affected by an access control bypass vulnerability
as referenced in security advisory SA0150.

  - On affected releases of Arista EOS configured as an 802.1X authenticator with per-supplicant access control
    lists, the ACL assigned to an authenticated supplicant may not be applied as intended, allowing an
    adjacent attacker to send traffic that should have been denied. (CVE-2026-77191)

Note that Nessus has not checked the 802.1X authenticator and per-supplicant ACL configuration required for
exposure and has instead relied only on the application's self-reported version number.");
  # https://www.arista.com/en/support/advisories-notices/security-advisory/24706-security-advisory-0150
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?4f5cda50");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Arista Networks EOS 4.33.8M / 4.34.6M / 4.35.1F or later, or apply the mitigation referenced in the
vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:A/AC:H/Au:S/C:N/I:P/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-77191");

  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:"2026/09/09");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/09/09");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/16");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"combined");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:arista:eos");
  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("arista_eos_detect.nbin");
  script_require_keys("Host/Arista-EOS/Version", "Settings/ParanoidReport");

  exit(0);
}

include('arista_eos_func.inc');
include('audit.inc');

# Exposure requires EOS to be configured as an 802.1X authenticator with per-supplicant ACLs. That configuration
# cannot be confirmed from the version alone, so require paranoid reporting.
if (report_paranoia < 2)
  audit(AUDIT_PARANOID);

var version = get_kb_item_or_exit('Host/Arista-EOS/Version');

# SA0150 lists the AWE 5000 and AWE 7200R series, CloudEOS, cEOS-lab, vEOS-lab and CloudVision eXchange as NOT
# affected; the vulnerability applies to the physical switch platforms only. The model KB is best-effort (it is
# derived from the startup-config or /etc/prefdl), so only gate when it is actually available -- otherwise the
# version check still applies.
var model = get_kb_item('Host/Arista-EOS/model');
if (!empty_or_null(model))
{
  model = toupper(model);
  if (model =~ "AWE-?5[0-9]{3}" || model =~ "AWE-?7[0-9]{3}R" || model =~ "CLOUDEOS" || model =~ "CEOS" ||
      model =~ "VEOS" || model =~ "CVX")
    audit(AUDIT_HOST_NOT, 'an affected model');
}

var vmatrix = make_array();

# Affected Software, per SA0150 for CVE-2026-77191. The advisory names 4.35.0.3F, 4.34.5M and 4.33.7.1M as the last
# affected releases of their respective trains, and all releases prior to 4.33 are affected in their entirety. The
# caps are extended with .9999 so intra-release maintenance builds below the named fix remain in range.
vmatrix['all'] = make_list('0.0<=4.32.9999',
                           '4.33.0<=4.33.7.9999',
                           '4.34.0<=4.34.5.9999',
                           '4.35.0<=4.35.0.9999');
vmatrix['fix'] = '4.33.8M / 4.34.6M / 4.35.1F';

if (eos_is_affected(vmatrix:vmatrix, version:version))
  security_report_v4(severity:SECURITY_NOTE, port:0, extra:eos_report_get());
else
  audit(AUDIT_INST_VER_NOT_VULN, 'Arista Networks EOS', version);