CVE-2025-40815 Overview
CVE-2025-40815 is a buffer overflow vulnerability [CWE-120] affecting all versions of the Siemens LOGO! 8 (BA2) programmable logic controller family and the SIPLUS LOGO! variants. The affected devices do not properly validate the structure of Transmission Control Protocol (TCP) packets in several internal handler methods. An attacker who can reach the device over the network can corrupt memory, take control of the instruction counter, and execute arbitrary code on the controller.
Critical Impact
Successful exploitation allows arbitrary code execution on industrial controllers used in automation deployments, with full loss of confidentiality, integrity, and availability of the affected device.
Affected Products
- Siemens LOGO! 12/24RCE, 12/24RCEo, 230RCE, 230RCEo, 24CE, 24CEo, 24RCE, 24RCEo (BA2 hardware, all versions)
- SIPLUS LOGO! 12/24RCE, 12/24RCEo, 230RCE, 230RCEo (BA2 hardware, all versions)
- SIPLUS LOGO! 24CE, 24CEo, 24RCE, 24RCEo (BA2 hardware, all versions)
Discovery Timeline
- 2025-11-11 - CVE-2025-40815 published to the National Vulnerability Database (NVD)
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-40815
Vulnerability Analysis
The flaw resides in the TCP packet handling logic of the LOGO! 8 BA2 firmware. Several internal methods consume fields from inbound TCP packets without validating length or structural constraints. When a malformed or oversized packet is processed, the routine writes beyond the bounds of a fixed-size buffer on the stack or heap. This memory corruption can overwrite saved return addresses or function pointers, transferring execution flow to attacker-controlled data.
The LOGO! 8 controllers are deployed in building automation, machine control, and small industrial process applications. Compromise of the device gives an attacker direct influence over connected actuators, sensors, and downstream control logic.
Root Cause
The vulnerability is a classic buffer copy without checking the size of the input [CWE-120]. The affected parsing methods trust packet-supplied length or content fields and do not enforce upper bounds before copying data into internal buffers. There is no canary, bounds check, or structural validator between the TCP receive path and the destination memory region.
Attack Vector
Exploitation requires network reachability to the LOGO! device and authenticated access at a high privilege level. An attacker meeting these prerequisites sends a crafted TCP packet whose length or field values exceed what the parser expects. The overflow corrupts adjacent memory, including the saved instruction pointer, allowing redirection of execution to a payload staged in the same packet or in subsequent traffic.
No verified public proof-of-concept code is available. The vulnerability mechanism is described in the Siemens Security Advisory SSA-267056.
Detection Methods for CVE-2025-40815
Indicators of Compromise
- Unexpected TCP traffic to LOGO! controller management ports from non-engineering workstations or external IP ranges.
- Abnormal controller reboots, watchdog resets, or transitions between RUN and STOP states without a corresponding operator action.
- Configuration or program block changes on the LOGO! device with no matching change ticket in the engineering workflow.
Detection Strategies
- Deploy an Operational Technology (OT)-aware network intrusion detection sensor that decodes the Siemens LOGO! TCP protocol and flags malformed or oversized packets.
- Baseline normal communication patterns between LOGO! Soft Comfort engineering stations and controllers, then alert on deviations in source, port, or payload size.
- Correlate controller availability events with network packet captures to identify reset-inducing traffic patterns.
Monitoring Recommendations
- Forward firewall and OT segmentation logs that border the LOGO! network segment to a centralized log platform for retention and analysis.
- Monitor for new TCP sessions targeting LOGO! devices that originate outside the engineering or maintenance VLAN.
- Track firmware version and configuration hashes of each LOGO! controller to identify unauthorized modification.
How to Mitigate CVE-2025-40815
Immediate Actions Required
- Restrict network access to LOGO! controllers so only authorized engineering workstations can reach the device over TCP.
- Place LOGO! devices behind a properly configured industrial firewall and within a dedicated control network segment.
- Disable or block remote access paths to LOGO! controllers from corporate networks or the internet.
- Review and rotate engineering passwords on LOGO! devices, since exploitation requires high-privilege access.
Patch Information
Refer to the Siemens Security Advisory SSA-267056 for the latest fix status and firmware availability for each affected LOGO! 8 BA2 and SIPLUS LOGO! model. At publication, all listed versions are reported as affected.
Workarounds
- Apply Siemens' operational guidelines for industrial security and follow the recommendations in the IEC 62443 standard for network segmentation and defense in depth.
- Use a hardened jump host and VPN with multi-factor authentication for any remote engineering access to LOGO! devices.
- Disable unused TCP services and management interfaces on the LOGO! controller when possible.
# Example firewall rule restricting LOGO! TCP access to engineering subnet only
# Replace 10.20.30.0/24 with the engineering VLAN and 10.40.50.10 with the LOGO! IP
iptables -A FORWARD -p tcp -d 10.40.50.10 -s 10.20.30.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 10.40.50.10 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
