CVE-2025-24811: Siemens SIMATIC S7-1200 DoS Vulnerability

CVE-2025-24811 Overview

A denial of service vulnerability has been identified in multiple Siemens SIMATIC S7-1200 and SIPLUS S7-1200 CPU models. The affected devices do not correctly process certain specially crafted packets sent to port 80/tcp, allowing an unauthenticated remote attacker to cause a denial of service condition on the target device. This vulnerability is classified under CWE-404 (Improper Resource Shutdown or Release).

Critical Impact
An unauthenticated attacker can remotely disrupt industrial control system operations by sending malformed packets to the web server interface, potentially causing production downtime and safety concerns in critical infrastructure environments.

Affected Products

SIMATIC S7-1200 CPU 1211C (all variants: AC/DC/Rly, DC/DC/DC, DC/DC/Rly)
SIMATIC S7-1200 CPU 1212C, 1212FC (all variants)
SIMATIC S7-1200 CPU 1214C, 1214FC, 1215C, 1215FC, 1217C (all variants)
SIPLUS S7-1200 CPU 1212, 1214, 1215 series (all variants including RAIL models)

Discovery Timeline

2025-02-11 - CVE-2025-24811 published to NVD
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-24811

Vulnerability Analysis

This vulnerability affects the web server component running on port 80/tcp of Siemens SIMATIC S7-1200 and SIPLUS S7-1200 programmable logic controllers (PLCs). The devices fail to properly handle malformed HTTP packets, leading to improper resource shutdown or release (CWE-404). When the PLC receives specially crafted network traffic on its web interface, the device enters a denial of service state, disrupting normal operations.

The vulnerability is particularly concerning in industrial control system (ICS) environments where SIMATIC S7-1200 PLCs are commonly deployed for automation tasks in manufacturing, utilities, and critical infrastructure. An attacker with network access to the PLC's web interface can exploit this flaw without requiring any authentication credentials.

Root Cause

The root cause of this vulnerability lies in improper resource management within the web server implementation on affected Siemens PLCs. The firmware does not adequately validate and handle certain malformed HTTP packets, resulting in a failure to properly release or manage resources when processing these packets. This leads to a denial of service condition where the device becomes unresponsive or requires a manual restart to recover normal operation.

Attack Vector

The attack can be executed remotely over the network by any unauthenticated attacker who has access to the PLC's web interface on port 80/tcp. The attack requires:

Network connectivity to the target PLC's TCP port 80
The ability to send specially crafted HTTP packets to the device
No authentication or user interaction is required

The attack complexity is low, making this vulnerability accessible to attackers with basic network access to the industrial control system network. Organizations with exposed or poorly segmented OT networks are at heightened risk.

Detection Methods for CVE-2025-24811

Indicators of Compromise

Unexpected PLC restart events or unresponsive devices
Anomalous HTTP traffic patterns targeting port 80/tcp on S7-1200 controllers
Multiple malformed HTTP requests from unfamiliar source IP addresses
Device diagnostic logs indicating web server crashes or resource exhaustion

Detection Strategies

Deploy network intrusion detection systems (NIDS) to monitor HTTP traffic destined for S7-1200 PLCs
Configure alerts for unusual connection patterns or traffic volumes to port 80/tcp on ICS devices
Implement deep packet inspection to identify malformed HTTP packets targeting PLC web servers
Monitor PLC status and availability through SCADA/HMI systems for unexpected state changes

Monitoring Recommendations

Enable comprehensive logging on network firewalls protecting OT network segments
Configure SIEM solutions to correlate events related to PLC connectivity and availability
Establish baseline network behavior for S7-1200 devices and alert on deviations
Regularly review access logs for the PLC web interface to identify reconnaissance or attack attempts

How to Mitigate CVE-2025-24811

Immediate Actions Required

Apply firmware updates from Siemens as soon as they become available
Restrict network access to port 80/tcp on affected PLCs using firewalls or access control lists
Implement network segmentation to isolate ICS devices from general corporate networks
Disable the web server interface if not required for operational purposes

Patch Information

Siemens has published a security advisory addressing this vulnerability. Organizations should consult the Siemens Security Advisory SSA-224824 for detailed patch information and firmware update instructions specific to their affected product models.

Workarounds

Implement strict network access controls limiting access to port 80/tcp to authorized management stations only
Deploy industrial firewalls or DMZ architectures to protect S7-1200 PLCs from untrusted network traffic
Use VPN connections for remote access to PLC web interfaces instead of direct network exposure
Consider disabling the web server functionality on PLCs where it is not operationally required

bash

# Example firewall rule to restrict access to S7-1200 web interface
# Allow only specific management workstation to access PLC web interface
iptables -A INPUT -p tcp --dport 80 -s 10.100.50.10 -d 10.200.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -d 10.200.0.0/24 -j DROP