Siemens SIMATIC S7-1500 Improper Check for Unusual or Exceptional Conditions (CVE-2026-22796)

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

include('compat.inc');

if (description)
{
  script_id(505146);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/02/16");

  script_cve_id("CVE-2026-22796");

  script_name(english:"Siemens SIMATIC S7-1500 Improper Check for Unusual or Exceptional Conditions (CVE-2026-22796)");

  script_set_attribute(attribute:"synopsis", value:
"The remote OT asset is affected by a vulnerability.");
  script_set_attribute(attribute:"description", value:
"Issue summary: A type confusion vulnerability exists in the signature
verification of signed PKCS#7 data where an ASN1_TYPE union member is
accessed without first validating the type, causing an invalid or NULL
pointer dereference when processing malformed PKCS#7 data.  Impact
summary: An application performing signature verification of PKCS#7
data or calling directly the PKCS7_digest_from_attributes() function
can be caused to dereference an invalid or NULL pointer when reading,
resulting in a Denial of Service.  The function
PKCS7_digest_from_attributes() accesses the message digest attribute
value without validating its type. When the type is not
V_ASN1_OCTET_STRING, this results in accessing invalid memory through
the ASN1_TYPE union, causing a crash.  Exploiting this vulnerability
requires an attacker to provide a malformed signed PKCS#7 to an
application that verifies it. The impact of the exploit is just a
Denial of Service, the PKCS7 API is legacy and applications should be
using the CMS API instead. For these reasons the issue was assessed as
Low severity.  The FIPS modules in 3.5, 3.4, 3.3 and 3.0 are not
affected by this issue, as the PKCS#7 parsing implementation is
outside the OpenSSL FIPS module boundary.  OpenSSL 3.6, 3.5, 3.4, 3.3,
3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.");
  script_set_attribute(attribute:"see_also", value:"https://cert-portal.siemens.com/productcert/html/ssa-265688.html");
  script_set_attribute(attribute:"solution", value:
"Refer to the vendor advisory.");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-22796");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_cwe_id(754);

  script_set_attribute(attribute:"vuln_publication_date", value:"2024/04/09");
  script_set_attribute(attribute:"patch_publication_date", value:"2024/04/09");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/02/13");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:siemens:simatic_s7-1500_tm_mfp");
  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/Siemens");

  exit(0);
}


include('tenable_ot_cve_funcs.inc');

get_kb_item_or_exit('Tenable.ot/Siemens');

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

var vuln_cpes = {
    "cpe:/o:siemens:simatic_s7-1500_tm_mfp" :
        {"versionEndIncluding" : "1.1", "versionStartIncluding" : "1.1", "family" : "S71500", "orderNumbers": ["6ES7558-1AA00-0AB0"]}
};

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