CVE-2025-11779: Circutor SGE-PLC Buffer Overflow Vulnerability

CVE-2025-11779 Overview

CVE-2025-11779 is a critical stack-based buffer overflow vulnerability affecting Circutor SGE-PLC1000 and SGE-PLC50 programmable logic controllers running firmware version 9.0.2. The vulnerability exists in the SetLan function, which is invoked when a new configuration is applied through the management web interface. When users make changes via the index.cgi web application, the function fails to properly sanitize input parameters, creating conditions for both buffer overflow exploitation and command injection attacks.

This vulnerability is particularly concerning for industrial control system (ICS) and operational technology (OT) environments where these PLCs are deployed for energy monitoring and power management applications. The adjacent network attack vector means that attackers with network access to the device segment can exploit this vulnerability without user interaction.

Critical Impact

With a CVSS 4.0 score of 9.4 (Critical), this vulnerability allows attackers with low privileges on an adjacent network to achieve complete compromise of the affected device, potentially leading to full control over industrial automation systems, data exfiltration, and lateral movement within OT networks.

Affected Products

• Circutor SGE-PLC1000 Firmware v9.0.2
• Circutor SGE-PLC1000 Hardware
• Circutor SGE-PLC50 Firmware v9.0.2
• Circutor SGE-PLC50 Hardware

Discovery Timeline

• 2025-12-02 - CVE-2025-11779 published to NVD
• 2025-12-03 - Last updated in NVD database

Technical Details for CVE-2025-11779

Vulnerability Analysis

The vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption vulnerability that occurs when a program writes data beyond the boundaries of a fixed-length buffer allocated on the stack. In the context of CVE-2025-11779, the SetLan function within the Circutor PLC firmware fails to validate the length of input parameters received from web requests before copying them into stack-allocated buffers.

The CVSS 4.0 vector string CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H indicates:

• Attack Vector (AV:A): Adjacent network access required
• Attack Complexity (AC:L): Low complexity to exploit
• Privileges Required (PR:L): Low-level authentication needed
• User Interaction (UI:N): No user interaction required
• Impact: High confidentiality, integrity, and availability impact on both the vulnerable system and subsequent systems

The EPSS (Exploit Prediction Scoring System) data shows a 2.122% probability of exploitation within the next 30 days, placing this vulnerability in the 83.649th percentile—indicating it has a higher likelihood of exploitation compared to most vulnerabilities.

Root Cause

The root cause of this vulnerability stems from improper input validation in the SetLan function of the device's web management interface. When configuration changes are submitted through the index.cgi web application, the function processes user-supplied parameters without adequate bounds checking or sanitization. This allows an attacker to supply oversized input that overflows the stack buffer, potentially overwriting the return address and other critical stack data.

The lack of input sanitization also introduces a secondary command injection vector, where maliciously crafted input could be interpreted as shell commands by the underlying system.

Attack Vector

The attack requires adjacent network access, meaning the attacker must be on the same network segment as the target device. This is common in industrial environments where PLCs are deployed on isolated OT networks. An attacker with low-level credentials to the web management interface can exploit this vulnerability by:

1. Authenticating to the index.cgi web application with valid credentials
2. Navigating to network configuration settings that invoke the SetLan function
3. Submitting maliciously crafted parameters that exceed expected buffer sizes
4. Triggering the buffer overflow to gain code execution or inject commands

The vulnerability does not require any user interaction beyond the attacker's own actions, making it highly exploitable once network access is obtained.

Detection Methods for CVE-2025-11779

Indicators of Compromise

• Unexpected network configuration changes on SGE-PLC1000 or SGE-PLC50 devices
• Anomalous HTTP POST requests to index.cgi with oversized parameters
• Unusual process execution or shell activity originating from the PLC management interface
• System crashes or unexpected reboots of affected PLC devices
• Log entries showing failed or suspicious authentication attempts followed by configuration changes

Detection Strategies

Organizations should implement multiple layers of detection to identify potential exploitation attempts:

Network-Based Detection:
Monitor network traffic to and from Circutor PLC devices for HTTP requests to index.cgi containing abnormally long parameter values. IDS/IPS signatures can be developed to flag requests where network configuration parameters exceed reasonable lengths.

Log Analysis:
Review web server logs on the affected devices for patterns indicating buffer overflow attempts, including malformed requests, unusually long URI or POST body lengths, and requests containing shell metacharacters.

Behavioral Monitoring:
Deploy endpoint detection solutions capable of monitoring embedded systems for unexpected process spawning, file system modifications, or network connections that could indicate successful exploitation.

Monitoring Recommendations

• Configure network segmentation to isolate PLC devices and monitor all traffic crossing segment boundaries
• Implement deep packet inspection for HTTP traffic destined for industrial control devices
• Enable comprehensive logging on the web management interface and forward logs to a centralized SIEM
• Deploy anomaly detection to baseline normal device behavior and alert on deviations
• Monitor for reconnaissance activity targeting the management web interface

How to Mitigate CVE-2025-11779

Immediate Actions Required

• Restrict network access to affected SGE-PLC1000 and SGE-PLC50 devices to only authorized management stations
• Implement network segmentation to isolate PLCs from general network access
• Disable web management interface if not operationally required
• Apply firewall rules to block unauthorized access to the index.cgi application
• Review and strengthen authentication credentials for all management accounts
• Monitor for any indicators of compromise detailed above

Patch Information

Organizations should consult the INCIBE-CERT security advisory for the latest patch information and remediation guidance from Circutor. The advisory is available at: https://www.incibe.es/en/incibe-cert/notices/aviso-sci/multiple-vulnerabilities-circutor-products-0

Contact Circutor directly for firmware updates addressing this vulnerability. Until patches are applied, implement compensating controls to reduce risk exposure.

Workarounds

If patching is not immediately possible, organizations should implement the following compensating controls:

Network Isolation:
Place affected devices on isolated network segments with strict access controls. Only allow connections from designated management workstations.

Web Interface Restrictions:
If the web management interface cannot be disabled entirely, restrict access using firewall rules to permit only specific source IP addresses. Consider implementing a web application firewall (WAF) to filter malicious requests.

Access Control Hardening:
Enforce strong authentication for the web interface, implement account lockout policies, and regularly rotate credentials. Consider implementing multi-factor authentication if supported by network architecture.