Siemens SIMATIC S7-1500 NULL Pointer Dereference (CVE-2025-38468)

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

include('compat.inc');

if (description)
{
  script_id(505245);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/03/24");

  script_cve_id("CVE-2025-38468");

  script_name(english:"Siemens SIMATIC S7-1500 NULL Pointer Dereference (CVE-2025-38468)");

  script_set_attribute(attribute:"synopsis", value:
"The remote OT asset is affected by a vulnerability.");
  script_set_attribute(attribute:"description", value:
"In the Linux kernel, the following vulnerability has been resolved:
net/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree
htb_lookup_leaf has a BUG_ON that can trigger with the following:
tc qdisc del dev lo root  tc qdisc add dev lo root handle 1: htb
default 1  tc class add dev lo parent 1: classid 1:1 htb rate 64bit
tc qdisc add dev lo parent 1:1 handle 2: netem  tc qdisc add dev lo
parent 2:1 handle 3: blackhole  ping -I lo -c1 -W0.001 127.0.0.1
The root cause is the following:    1. htb_dequeue calls
htb_dequeue_tree which calls the dequeue handler on     the selected
leaf qdisc  2. netem_dequeue calls enqueue on the child qdisc  3.
blackhole_enqueue drops the packet and returns a value that is not
just NET_XMIT_SUCCESS  4. Because of this, netem_dequeue calls
qdisc_tree_reduce_backlog, and     since qlen is now 0, it calls
htb_qlen_notify -> htb_deactivate ->     htb_deactiviate_prios ->
htb_remove_class_from_row -> htb_safe_rb_erase  5. As this is the only
class in the selected hprio rbtree,     __rb_change_child in
__rb_erase_augmented sets the rb_root pointer to     NULL  6. Because
blackhole_dequeue returns NULL, netem_dequeue returns NULL,     which
causes htb_dequeue_tree to call htb_lookup_leaf with the same
hprio rbtree, and fail the BUG_ON    The function graph for this
scenario is shown here:   0)               |  htb_enqueue() {   0) +
13.635 us   |    netem_enqueue();   0)   4.719 us    |
htb_activate_prios();   0) # 2249.199 us |  }   0)               |
htb_dequeue() {   0)   2.355 us    |    htb_lookup_leaf();   0)
|    netem_dequeue() {   0) + 11.061 us   |      blackhole_enqueue();
0)               |      qdisc_tree_reduce_backlog() {   0)
|        qdisc_lookup_rcu() {   0)   1.873 us    |
qdisc_match_from_root();   0)   6.292 us    |        }   0)   1.894 us
|        htb_search();   0)               |        htb_qlen_notify() {
0)   2.655 us    |          htb_deactivate_prios();   0)   6.933 us
|        }   0) + 25.227 us   |      }   0)   1.983 us    |
blackhole_dequeue();   0) + 86.553 us   |    }   0) # 2932.761 us |
qdisc_warn_nonwc();   0)               |    htb_lookup_leaf() {   0)
|      BUG_ON();   ------------------------------------------    The
full original bug report can be seen here [1].    We can fix this just
by returning NULL instead of the BUG_ON,  as htb_dequeue_tree returns
NULL when htb_lookup_leaf returns  NULL.    [1]
https://lore.kernel.org/netdev/pF5XOOIim0IuEfhI-SOxTgRvNoDwuux7UHKnE_Y
5-
zVd4wmGvNk2ceHjKb8ORnzw0cGwfmVu42g9dL7XyJLf1NEzaztboTWcm0Ogxuojoeo=@wi
llsroot.io/

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-082556.html");
  script_set_attribute(attribute:"solution", value:
"Refer to the vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/C:N/I:N/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:L/PR:L/UI:N/S:U/C:N/I:N/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-2025-38468");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_cwe_id(476);

  script_set_attribute(attribute:"vuln_publication_date", value:"2025/06/10");
  script_set_attribute(attribute:"patch_publication_date", value:"2025/06/10");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/03/23");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:siemens:simatic_s7-1500_cpu_firmware:3.1.5");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:siemens:siplus_s7-1500_cpu_firmware");
  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_cpu_firmware:3.1.5" :
        {"versionStartIncluding" : "3.1.5", "family" : "S71500", "orderNumbers" : ['6ES7518-4AX00-1AB0', '6ES7518-4AX00-1AC0', '6ES7518-4FX00-1AB0', '6ES7518-4FX00-1AC0']},
    "cpe:/o:siemens:siplus_s7-1500_cpu_firmware" :
        {"family" : "S71500", "orderNumbers" : ['6AG1518-4AX00-4AC0']}
};

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