Siemens SIMATIC S7-1500 Use After Free (CVE-2025-39866)

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

include('compat.inc');

if (description)
{
  script_id(505168);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/07/17");

  script_cve_id("CVE-2025-39866");
  script_xref(name:"ICSA", value:"26-134-10");

  script_name(english:"Siemens SIMATIC S7-1500 Use After Free (CVE-2025-39866)");

  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: writeback: fix use-after-free in __mark_inode_dirty()    An use-
after-free issue occurred when __mark_inode_dirty() get the
bdi_writeback that was in the progress of switching.    CPU: 1 PID:
562 Comm: systemd-random- Not tainted 6.6.56-gb4403bd46a8e #1  ......
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)  pc :
__mark_inode_dirty+0x124/0x418  lr : __mark_inode_dirty+0x118/0x418
sp : ffffffc08c9dbbc0  ........  Call trace:
__mark_inode_dirty+0x124/0x418   generic_update_time+0x4c/0x60
file_modified+0xcc/0xd0   ext4_buffered_write_iter+0x58/0x124
ext4_file_write_iter+0x54/0x704   vfs_write+0x1c0/0x308
ksys_write+0x74/0x10c   __arm64_sys_write+0x1c/0x28
invoke_syscall+0x48/0x114   el0_svc_common.constprop.0+0xc0/0xe0
do_el0_svc+0x1c/0x28   el0_svc+0x40/0xe4
el0t_64_sync_handler+0x120/0x12c   el0t_64_sync+0x194/0x198    Root
cause is:    systemd-random-seed                         kworker
----------------------------------------------------------------------
___mark_inode_dirty                     inode_switch_wbs_work_fn
spin_lock(&inode->i_lock);    inode_attach_wb
locked_inode_to_wb_and_lock_list       get inode->i_wb
spin_unlock(&inode->i_lock);       spin_lock(&wb->list_lock)
spin_lock(&inode->i_lock)    inode_io_list_move_locked
spin_unlock(&wb->list_lock)    spin_unlock(&inode->i_lock)
spin_lock(&old_wb->list_lock)
inode_do_switch_wbs
spin_lock(&inode->i_lock)
inode->i_wb = new_wb
spin_unlock(&inode->i_lock)
spin_unlock(&old_wb->list_lock)
wb_put_many(old_wb, nr_switched)
cgwb_release                                        old wb released
wb_wakeup_delayed() accesses wb,    then trigger the use-after-free
issue    Fix this race condition by holding inode spinlock until
wb_wakeup_delayed() finished.

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:"see_also", value:"https://www.cisa.gov/news-events/ics-advisories/ICSA-26-134-10");
  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:POC/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:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2025-39866");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_cwe_id(416);

  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:"2026/02/16");

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

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