Siemens SIMATIC S7-1500 CPU 1518 MFP Use After Free (CVE-2025-39691)

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

include('compat.inc');

if (description)
{
  script_id(505640);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/07/29");

  script_cve_id("CVE-2025-39691");

  script_name(english:"Siemens SIMATIC S7-1500 CPU 1518 MFP Use After Free (CVE-2025-39691)");

  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:
fs/buffer: fix use-after-free when call bh_read() helper    There's
issue as follows:  BUG: KASAN: stack-out-of-bounds in
end_buffer_read_sync+0xe3/0x110  Read of size 8 at addr
ffffc9000168f7f8 by task swapper/3/0  CPU: 3 UID: 0 PID: 0 Comm:
swapper/3 Not tainted 6.16.0-862.14.0.6.x86_64  Hardware name: QEMU
Standard PC (i440FX + PIIX, 1996)  Call Trace:   <IRQ>
dump_stack_lvl+0x55/0x70
print_address_description.constprop.0+0x2c/0x390
print_report+0xb4/0x270   kasan_report+0xb8/0xf0
end_buffer_read_sync+0xe3/0x110   end_bio_bh_io_sync+0x56/0x80
blk_update_request+0x30a/0x720   scsi_end_request+0x51/0x2b0
scsi_io_completion+0xe3/0x480   ? scsi_device_unbusy+0x11e/0x160
blk_complete_reqs+0x7b/0x90   handle_softirqs+0xef/0x370
irq_exit_rcu+0xa5/0xd0   sysvec_apic_timer_interrupt+0x6e/0x90
</IRQ>     Above issue happens when do ntfs3 filesystem mount, issue
may happens   as follows:             mount
IRQ  ntfs_fill_super    read_cache_page      do_read_cache_folio
filemap_read_folio          mpage_read_folio
do_mpage_readpage            ntfs_get_block_vbo             bh_read
submit_bh               wait_on_buffer(bh);
blk_complete_reqs
scsi_io_completion
scsi_end_request
blk_update_request
end_bio_bh_io_sync
end_buffer_read_sync
__end_buffer_read_notouch
unlock_buffer                wait_on_buffer(bh);--> return will return
to caller                                              put_bh
--> trigger stack-out-of-bounds  In the mpage_read_folio() function,
the stack variable 'map_bh' is  passed to ntfs_get_block_vbo(). Once
unlock_buffer() unlocks and  wait_on_buffer() returns to continue
processing, the stack variable  is likely to be reclaimed.
Consequently, during the end_buffer_read_sync()  process, calling
put_bh() may result in stack overrun.    If the bh is not allocated on
the stack, it belongs to a folio.  Freeing  a buffer head which
belongs to a folio is done by drop_buffers() which  will fail to free
buffers which are still locked.  So it is safe to call  put_bh()
before __end_buffer_read_notouch().

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-019113.html");
  script_set_attribute(attribute:"see_also", value:"https://cert-portal.siemens.com/productcert/html/ssa-032379.html");
  script_set_attribute(attribute:"see_also", value:"https://support.industry.siemens.com/cs/ww/en/view/109814144/");
  script_set_attribute(attribute:"solution", value:
"Refer to the vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/C:C/I:C/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:H/I:H/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-2025-39691");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_cwe_id(416);

  script_set_attribute(attribute:"vuln_publication_date", value:"2025/09/05");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/05/12");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/07/27");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:siemens:simatic_s7-1500_cpu_firmware:3.1.6");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:siemens:siplus_s7-1500_cpu_firmware");
  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_cpu_firmware:3.1.6" :
        {"versionStartIncluding" : "3.1.6", "family" : "S71500", "orderNumbers" : ['6ES7518-4FX00-1AC0', '6ES7518-4AX00-1AB0', '6ES7518-4AX00-1AC0', '6ES7518-4FX00-1AB0']},
    "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);