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Cisco ASA Improper Neutralization of Special Elements in Output Used by a Downstream Component (CVE-2020-3561)

🗓️ 06 Oct 2026 00:00:00Reported by TenableType 
nessus
 nessus
🔗 www.tenable.com👁 5 Views

Unauthenticated remote CRLF injection in Cisco ASA and FTD Clientless SSL VPN.

Related
Refs
Code
#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(506186);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/07");

  script_cve_id("CVE-2020-3561");

  script_name(english:"Cisco ASA Improper Neutralization of Special Elements in Output Used by a Downstream Component (CVE-2020-3561)");

  script_set_attribute(attribute:"synopsis", value:
"The remote OT asset is affected by a vulnerability.");
  script_set_attribute(attribute:"description", value:
"A vulnerability in the Clientless SSL VPN (WebVPN) of Cisco Adaptive
Security Appliance (ASA) Software and Cisco Firepower Threat Defense
(FTD) Software could allow an unauthenticated, remote attacker to
inject arbitrary HTTP headers in the responses of the affected system.
The vulnerability is due to improper input sanitization. An attacker
could exploit this vulnerability by persuading a user of the interface
to click a crafted link. A successful exploit could allow the attacker
to conduct a CRLF injection attack, adding arbitrary HTTP headers in
the responses of the system and redirecting the user to arbitrary
websites.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.");
  # https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-crlf-inj-BX9uRwSn
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?f487e64d");
  script_set_attribute(attribute:"solution", value:
"Refer to the vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/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:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2020-3561");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_cwe_id(74, 93);

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/10/21");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/10/21");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/06");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:cisco:adaptive_security_appliance_software:9");
  script_set_attribute(attribute:"generated_plugin", value:"former");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Tenable.ot");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("tenable_ot_api_integration.nasl");
  script_require_keys("Tenable.ot/Cisco");

  exit(0);
}


include('tenable_ot_cve_funcs.inc');

get_kb_item_or_exit('Tenable.ot/Cisco');

var asset = tenable_ot::assets::get(vendor:'Cisco');

var vuln_cpes = {
    "cpe:/o:cisco:adaptive_security_appliance_software:9.8.0" :
        {"versionEndExcluding" : "9.8.4.20", "versionStartIncluding" : "9.8.0", "family" : "CiscoFirepower"},
    "cpe:/o:cisco:adaptive_security_appliance_software:9.9.0" :
        {"versionEndExcluding" : "9.9.2.80", "versionStartIncluding" : "9.9.0", "family" : "CiscoFirepower"},
    "cpe:/o:cisco:adaptive_security_appliance_software:9.10.0" :
        {"versionEndExcluding" : "9.10.1.43", "versionStartIncluding" : "9.10.0", "family" : "CiscoFirepower"},
    "cpe:/o:cisco:adaptive_security_appliance_software:9.12.0" :
        {"versionEndExcluding" : "9.12.3.9", "versionStartIncluding" : "9.12.0", "family" : "CiscoFirepower"},
    "cpe:/o:cisco:adaptive_security_appliance_software:9.13.0" :
        {"versionEndExcluding" : "9.13.1.10", "versionStartIncluding" : "9.13.0", "family" : "CiscoFirepower"},
    "cpe:/o:cisco:adaptive_security_appliance_software:9.14.0" :
        {"versionEndExcluding" : "9.14.1.10", "versionStartIncluding" : "9.14.0", "family" : "CiscoFirepower"}
};

tenable_ot::cve::compare_and_report(asset:asset, cpes:vuln_cpes, severity:SECURITY_WARNING);

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07 Oct 2026 00:00Current
6.5Medium risk
Vulners AI Score6.5
CVSS 24.3
CVSS 3.14.7
CVSS 34.7
EPSS0.0129
SSVC
5