CVE-2025-40816 Overview
CVE-2025-40816 affects Siemens LOGO! 8 series logic modules and their SIPLUS variants across all firmware versions. The devices fail to perform certain validations during network interactions. An unauthenticated attacker on an adjacent network can manipulate the device IP address, rendering the controller unreachable. The flaw maps to [CWE-306] Missing Authentication for Critical Function. Siemens disclosed the issue in advisory SSA-267056.
Critical Impact
Unauthenticated adjacent-network attackers can change the IP configuration of LOGO! programmable logic controllers (PLCs), disrupting industrial process visibility and control until the device is physically reconfigured.
Affected Products
- Siemens LOGO! 12/24RCE, 12/24RCEo, 230RCE, 230RCEo, 24CE, 24CEo, 24RCE, 24RCEo (all versions)
- SIPLUS LOGO! 12/24RCE, 12/24RCEo, 230RCE, 230RCEo (all versions)
- SIPLUS LOGO! 24CE, 24CEo, 24RCE, 24RCEo (all versions)
Discovery Timeline
- 2025-11-11 - CVE-2025-40816 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-40816
Vulnerability Analysis
The Siemens LOGO! 8 family is a compact programmable logic controller (PLC) used in small automation deployments such as building control, HVAC, and lighting. The affected modules expose network services for configuration and programming but do not authenticate or validate certain management requests before acting on them. An attacker on the same logical network segment can send crafted requests that overwrite the device IP address.
Once the IP is changed, engineering stations, SCADA frontends, and monitoring systems lose connectivity to the controller. The PLC continues to run its ladder logic, but operators cannot read telemetry, push program updates, or trigger remote stops. Recovery requires physical access to the device to reset network parameters, increasing downtime for distributed installations.
Root Cause
The root cause is missing authentication for a critical function [CWE-306]. The LOGO! firmware accepts network configuration changes without verifying the identity of the requester. No credential check, session token, or cryptographic validation gates the IP reassignment path.
Attack Vector
Exploitation requires adjacent network access, meaning the attacker must reach the same broadcast domain or routed segment as the controller. No user interaction or privileges are required. The attacker sends a configuration request to the LOGO! device, supplying an arbitrary IP address. The device applies the change without challenge, severing legitimate management sessions. No verified public proof-of-concept code is currently available for this vulnerability. Refer to the Siemens Security Advisory SSA-267056 for protocol-level details.
Detection Methods for CVE-2025-40816
Indicators of Compromise
- Unexpected IP address changes on LOGO! controllers reported by engineering workstations or asset inventory tools.
- Loss of connectivity between SCADA/HMI systems and one or more LOGO! PLCs without corresponding maintenance activity.
- ARP table changes on operational technology (OT) switches showing LOGO! MAC addresses bound to new IP addresses.
Detection Strategies
- Monitor OT network traffic for unsolicited configuration commands directed at LOGO! devices on TCP/UDP ports used by the LOGO! protocol.
- Correlate DHCP and ARP logs to identify unauthorized hosts issuing management traffic toward PLC subnets.
- Use passive industrial protocol analyzers to baseline LOGO! configuration messages and alert on deviations.
Monitoring Recommendations
- Enable network flow logging on switches and firewalls that segment the LOGO! subnet, retaining records for at least 90 days.
- Track device reachability with continuous ICMP and protocol-level health checks, alerting on sudden disappearance of LOGO! endpoints.
- Audit any host with management access to the OT segment for unauthorized scanning or configuration tooling.
How to Mitigate CVE-2025-40816
Immediate Actions Required
- Restrict access to LOGO! controllers to trusted engineering hosts using firewall and switch access control lists.
- Place LOGO! devices on dedicated VLANs isolated from corporate and general-purpose IT networks.
- Review the Siemens Security Advisory SSA-267056 for current vendor guidance.
- Inventory all LOGO! 8 and SIPLUS LOGO! modules and document their network exposure.
Patch Information
Siemens lists all versions of the affected LOGO! 8 and SIPLUS LOGO! product lines as vulnerable. No fixed firmware version is identified in the NVD record at publication. Operators should consult Siemens Security Advisory SSA-267056 for the latest remediation status and apply firmware updates when Siemens releases them.
Workarounds
- Apply Siemens defense-in-depth recommendations: operate the devices only within protected IT environments and behind industrial security appliances.
- Block adjacent-network access to LOGO! management ports using OT firewalls or unidirectional gateways where feasible.
- Disable or physically disconnect LOGO! Ethernet interfaces on units that do not require network connectivity.
- Implement network access control (802.1X) on OT switches to prevent unauthorized devices from joining the PLC segment.
# Example: restrict LOGO! subnet access at the firewall
# Permit only the engineering workstation to reach the LOGO! VLAN
iptables -A FORWARD -s 10.20.30.10/32 -d 10.20.40.0/24 -j ACCEPT
iptables -A FORWARD -d 10.20.40.0/24 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
